// 
pub mod solution {
//{"name":"uc23_k","group":"Manual","url":"","interactive":false,"timeLimit":2000,"tests":[{"input":"","output":""}],"testType":"single","input":{"type":"stdin","fileName":null,"pattern":null},"output":{"type":"stdout","fileName":null,"pattern":null},"languages":{"java":{"taskClass":"uc23_k"}}}

use crate::algo_lib::collections::min_max::MinimMaxim;
use crate::algo_lib::io::input::Input;
use crate::algo_lib::io::output::Output;

type PreCalc = ();

fn solve(input: &mut Input, out: &mut Output, _test_case: usize, _data: &PreCalc) {
let m = input.read_size();
let mut a = input.read_long_vec(m);
let mut b = input.read_long_vec(m);

a[0] = 1000_000_000;
b[0] = 1000_000_000;
let mut num_pairs = 0;
let mut num_pair_types = 0;
let mut max_a_in_pair = 0;
let mut max_b_in_pair = 0;
for i in 0..m {
let j = m - 1 - i;
let cur = a[i].min(b[j]);
if cur > 0 {
num_pairs += cur;
num_pair_types += 1;
max_a_in_pair.maxim(i);
max_b_in_pair.maxim(j);
a[i] -= cur;
b[j] -= cur;
}
}
let mut add = 0;
let mut at = 0;
for i in (0..m).rev() {
at.maxim(m - i);
while at < m {
if b[at] != 0 {
let cur = a[i].min(b[at]);
add += cur;
a[i] -= cur;
b[at] -= cur;
if a[i] == 0 {
break;
}
}
at += 1;
}
}
if add > 0 {
out.print_line(num_pairs + add);
return;
}
let mut max_a_free = 0;
for i in (1..m).rev() {
if a[i] != 0 {
max_a_free = i;
break;
}
}
let mut max_b_free = 0;
for i in (1..m).rev() {
if b[i] != 0 {
max_b_free = i;
break;
}
}
if max_a_in_pair + max_b_free >= m || max_b_in_pair + max_a_free >= m {
out.print_line(num_pairs);
return;
}
if num_pair_types > 1 {
out.print_line(num_pairs - 1);
return;
}
out.print_line(0);
}

pub(crate) fn run(mut input: Input, mut output: Output) -> bool {
let pre_calc = ();

#[allow(dead_code)]
enum TestType {
Single,
MultiNumber,
MultiEof,
}
let test_type = TestType::MultiNumber;
match test_type {
TestType::Single => solve(&mut input, &mut output, 1, &pre_calc),
TestType::MultiNumber => {
let t = input.read();
for i in 1..=t {
solve(&mut input, &mut output, i, &pre_calc);
}
}
TestType::MultiEof => {
let mut i = 1;
while input.peek().is_some() {
solve(&mut input, &mut output, i, &pre_calc);
i += 1;
}
}
}
output.flush();
input.skip_whitespace();
input.peek().is_none()
}

}
pub mod algo_lib {
pub mod collections {
pub mod min_max {
pub trait MinimMaxim<Rhs = Self>: PartialOrd + Sized {
fn minim(&mut self, other: Rhs) -> bool;

fn maxim(&mut self, other: Rhs) -> bool;
}

impl<T: PartialOrd> MinimMaxim for T {
fn minim(&mut self, other: Self) -> bool {
if other < *self {
*self = other;
true
} else {
false
}
}

fn maxim(&mut self, other: Self) -> bool {
if other > *self {
*self = other;
true
} else {
false
}
}
}

impl<T: PartialOrd> MinimMaxim<T> for Option<T> {
fn minim(&mut self, other: T) -> bool {
match self {
None => {
*self = Some(other);
true
}
Some(v) => v.minim(other),
}
}

fn maxim(&mut self, other: T) -> bool {
match self {
None => {
*self = Some(other);
true
}
Some(v) => v.maxim(other),
}
}
}
}
pub mod vec_ext {
pub mod default {
pub fn default_vec<T: Default>(len: usize) -> Vec<T> {
let mut v = Vec::with_capacity(len);
for _ in 0..len {
v.push(T::default());
}
v
}
}
}
}
pub mod io {
pub mod input {
use crate::algo_lib::collections::vec_ext::default::default_vec;
use std::io::Read;

pub struct Input<'s> {
input: &'s mut dyn Read,
buf: Vec<u8>,
at: usize,
buf_read: usize,
}

macro_rules! read_impl {
($t: ty, $read_name: ident, $read_vec_name: ident) => {
pub fn $read_name(&mut self) -> $t {
self.read()
}

pub fn $read_vec_name(&mut self, len: usize) -> Vec<$t> {
self.read_vec(len)
}
};

($t: ty, $read_name: ident, $read_vec_name: ident, $read_pair_vec_name: ident) => {
read_impl!($t, $read_name, $read_vec_name);

pub fn $read_pair_vec_name(&mut self, len: usize) -> Vec<($t, $t)> {
self.read_vec(len)
}
};
}

impl<'s> Input<'s> {
const DEFAULT_BUF_SIZE: usize = 4096;

pub fn new(input: &'s mut dyn Read) -> Self {
Self {
input,
buf: default_vec(Self::DEFAULT_BUF_SIZE),
at: 0,
buf_read: 0,
}
}

pub fn new_with_size(input: &'s mut dyn Read, buf_size: usize) -> Self {
Self {
input,
buf: default_vec(buf_size),
at: 0,
buf_read: 0,
}
}

pub fn get(&mut self) -> Option<u8> {
if self.refill_buffer() {
let res = self.buf[self.at];
self.at += 1;
if res == b'\r' {
if self.refill_buffer() && self.buf[self.at] == b'\n' {
self.at += 1;
}
return Some(b'\n');
}
Some(res)
} else {
None
}
}

pub fn peek(&mut self) -> Option<u8> {
if self.refill_buffer() {
let res = self.buf[self.at];
Some(if res == b'\r' { b'\n' } else { res })
} else {
None
}
}

pub fn skip_whitespace(&mut self) {
while let Some(b) = self.peek() {
if !char::from(b).is_whitespace() {
return;
}
self.get();
}
}

pub fn next_token(&mut self) -> Option<Vec<u8>> {
self.skip_whitespace();
let mut res = Vec::new();
while let Some(c) = self.get() {
if char::from(c).is_whitespace() {
break;
}
res.push(c);
}
if res.is_empty() {
None
} else {
Some(res)
}
}

//noinspection RsSelfConvention
pub fn is_exhausted(&mut self) -> bool {
self.peek().is_none()
}

//noinspection RsSelfConvention
pub fn is_empty(&mut self) -> bool {
self.skip_whitespace();
self.is_exhausted()
}

pub fn read<T: Readable>(&mut self) -> T {
T::read(self)
}

pub fn read_vec<T: Readable>(&mut self, size: usize) -> Vec<T> {
let mut res = Vec::with_capacity(size);
for _ in 0..size {
res.push(self.read());
}
res
}

pub fn read_char(&mut self) -> char {
self.skip_whitespace();
self.get().unwrap().into()
}

read_impl!(u32, read_unsigned, read_unsigned_vec);
read_impl!(u64, read_u64, read_u64_vec);
read_impl!(usize, read_size, read_size_vec, read_size_pair_vec);
read_impl!(i32, read_int, read_int_vec, read_int_pair_vec);
read_impl!(i64, read_long, read_long_vec, read_long_pair_vec);
read_impl!(i128, read_i128, read_i128_vec);

fn refill_buffer(&mut self) -> bool {
if self.at == self.buf_read {
self.at = 0;
self.buf_read = self.input.read(&mut self.buf).unwrap();
self.buf_read != 0
} else {
true
}
}
}

pub trait Readable {
fn read(input: &mut Input) -> Self;
}

impl Readable for char {
fn read(input: &mut Input) -> Self {
input.read_char()
}
}

impl<T: Readable> Readable for Vec<T> {
fn read(input: &mut Input) -> Self {
let size = input.read();
input.read_vec(size)
}
}

macro_rules! read_integer {
($($t:ident)+) => {$(
impl Readable for $t {
fn read(input: &mut Input) -> Self {
input.skip_whitespace();
let mut c = input.get().unwrap();
let sgn = match c {
b'-' => {
c = input.get().unwrap();
true
}
b'+' => {
c = input.get().unwrap();
false
}
_ => false,
};
let mut res = 0;
loop {
assert!(c.is_ascii_digit());
res *= 10;
let d = (c - b'0') as $t;
if sgn {
res -= d;
} else {
res += d;
}
match input.get() {
None => break,
Some(ch) => {
if ch.is_ascii_whitespace() {
break;
} else {
c = ch;
}
}
}
}
res
}
}
)+};
}

read_integer!(i8 i16 i32 i64 i128 isize u8 u16 u32 u64 u128 usize);

macro_rules! tuple_readable {
($($name:ident)+) => {
impl<$($name: Readable), +> Readable for ($($name,)+) {
fn read(input: &mut Input) -> Self {
($($name::read(input),)+)
}
}
}
}

tuple_readable! {T}
tuple_readable! {T U}
tuple_readable! {T U V}
tuple_readable! {T U V X}
tuple_readable! {T U V X Y}
tuple_readable! {T U V X Y Z}
tuple_readable! {T U V X Y Z A}
tuple_readable! {T U V X Y Z A B}
tuple_readable! {T U V X Y Z A B C}
tuple_readable! {T U V X Y Z A B C D}
tuple_readable! {T U V X Y Z A B C D E}
tuple_readable! {T U V X Y Z A B C D E F}

impl Read for Input<'_> {
fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
if self.at == self.buf_read {
self.input.read(buf)
} else {
let mut i = 0;
while i < buf.len() && self.at < self.buf_read {
buf[i] = self.buf[self.at];
i += 1;
self.at += 1;
}
Ok(i)
}
}
}
}
pub mod output {
use crate::algo_lib::collections::vec_ext::default::default_vec;
use std::io::stderr;
use std::io::Stderr;
use std::io::Write;

#[derive(Copy, Clone)]
pub enum BoolOutput {
YesNo,
YesNoCaps,
PossibleImpossible,
Custom(&'static str, &'static str),
}

impl BoolOutput {
pub fn output(&self, output: &mut Output, val: bool) {
(if val { self.yes() } else { self.no() }).write(output);
}

fn yes(&self) -> &str {
match self {
BoolOutput::YesNo => "Yes",
BoolOutput::YesNoCaps => "YES",
BoolOutput::PossibleImpossible => "Possible",
BoolOutput::Custom(yes, _) => yes,
}
}

fn no(&self) -> &str {
match self {
BoolOutput::YesNo => "No",
BoolOutput::YesNoCaps => "NO",
BoolOutput::PossibleImpossible => "Impossible",
BoolOutput::Custom(_, no) => no,
}
}
}

pub struct Output<'s> {
output: &'s mut dyn Write,
buf: Vec<u8>,
at: usize,
auto_flush: bool,
bool_output: BoolOutput,
}

impl<'s> Output<'s> {
const DEFAULT_BUF_SIZE: usize = 4096;

pub fn new(output: &'s mut dyn Write) -> Self {
Self {
output,
buf: default_vec(Self::DEFAULT_BUF_SIZE),
at: 0,
auto_flush: false,
bool_output: BoolOutput::YesNoCaps,
}
}

pub fn new_with_auto_flush(output: &'s mut dyn Write) -> Self {
Self {
output,
buf: default_vec(Self::DEFAULT_BUF_SIZE),
at: 0,
auto_flush: true,
bool_output: BoolOutput::YesNoCaps,
}
}

pub fn flush(&mut self) {
if self.at != 0 {
self.output.write_all(&self.buf[..self.at]).unwrap();
self.output.flush().unwrap();
self.at = 0;
}
}

pub fn print<T: Writable>(&mut self, s: T) {
s.write(self);
self.maybe_flush();
}

pub fn print_line<T: Writable>(&mut self, s: T) {
self.print(s);
self.put(b'\n');
self.maybe_flush();
}

pub fn put(&mut self, b: u8) {
self.buf[self.at] = b;
self.at += 1;
if self.at == self.buf.len() {
self.flush();
}
}

pub fn maybe_flush(&mut self) {
if self.auto_flush {
self.flush();
}
}

pub fn print_per_line<T: Writable>(&mut self, arg: &[T]) {
for i in arg {
i.write(self);
self.put(b'\n');
}
}

pub fn print_iter<T: Writable, I: Iterator<Item = T>>(&mut self, iter: I) {
let mut first = true;
for e in iter {
if first {
first = false;
} else {
self.put(b' ');
}
e.write(self);
}
}

pub fn print_iter_ref<'a, T: 'a + Writable, I: Iterator<Item = &'a T>>(&mut self, iter: I) {
let mut first = true;
for e in iter {
if first {
first = false;
} else {
self.put(b' ');
}
e.write(self);
}
}

pub fn set_bool_output(&mut self, bool_output: BoolOutput) {
self.bool_output = bool_output;
}
}

impl Write for Output<'_> {
fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
let mut start = 0usize;
let mut rem = buf.len();
while rem > 0 {
let len = (self.buf.len() - self.at).min(rem);
self.buf[self.at..self.at + len].copy_from_slice(&buf[start..start + len]);
self.at += len;
if self.at == self.buf.len() {
self.flush();
}
start += len;
rem -= len;
}
self.maybe_flush();
Ok(buf.len())
}

fn flush(&mut self) -> std::io::Result<()> {
self.flush();
Ok(())
}
}

pub trait Writable {
fn write(&self, output: &mut Output);
}

impl Writable for &str {
fn write(&self, output: &mut Output) {
output.write_all(self.as_bytes()).unwrap();
}
}

impl Writable for String {
fn write(&self, output: &mut Output) {
output.write_all(self.as_bytes()).unwrap();
}
}

impl Writable for char {
fn write(&self, output: &mut Output) {
output.put(*self as u8);
}
}

impl<T: Writable> Writable for [T] {
fn write(&self, output: &mut Output) {
output.print_iter_ref(self.iter());
}
}

impl<T: Writable, const N: usize> Writable for [T; N] {
fn write(&self, output: &mut Output) {
output.print_iter_ref(self.iter());
}
}

impl<T: Writable> Writable for &T {
fn write(&self, output: &mut Output) {
T::write(self, output)
}
}

impl<T: Writable> Writable for Vec<T> {
fn write(&self, output: &mut Output) {
self.as_slice().write(output);
}
}

impl Writable for () {
fn write(&self, _output: &mut Output) {}
}

macro_rules! write_to_string {
($($t:ident)+) => {$(
impl Writable for $t {
fn write(&self, output: &mut Output) {
self.to_string().write(output);
}
}
)+};
}

write_to_string!(u8 u16 u32 u64 u128 usize i8 i16 i32 i64 i128 isize);

macro_rules! tuple_writable {
($name0:ident $($name:ident: $id:tt )*) => {
impl<$name0: Writable, $($name: Writable,)*> Writable for ($name0, $($name,)*) {
fn write(&self, out: &mut Output) {
self.0.write(out);
$(
out.put(b' ');
self.$id.write(out);
)*
}
}
}
}

tuple_writable! {T}
tuple_writable! {T U:1}
tuple_writable! {T U:1 V:2}
tuple_writable! {T U:1 V:2 X:3}
tuple_writable! {T U:1 V:2 X:3 Y:4}
tuple_writable! {T U:1 V:2 X:3 Y:4 Z:5}
tuple_writable! {T U:1 V:2 X:3 Y:4 Z:5 A:6}
tuple_writable! {T U:1 V:2 X:3 Y:4 Z:5 A:6 B:7}

impl<T: Writable> Writable for Option<T> {
fn write(&self, output: &mut Output) {
match self {
None => (-1).write(output),
Some(t) => t.write(output),
}
}
}

impl Writable for bool {
fn write(&self, output: &mut Output) {
let bool_output = output.bool_output;
bool_output.output(output, *self)
}
}

static mut ERR: Option<Stderr> = None;
pub fn err() -> Output<'static> {
unsafe {
if ERR.is_none() {
ERR = Some(stderr());
}
Output::new_with_auto_flush(ERR.as_mut().unwrap())
}
}
}
}
}
fn main() {
    let mut sin = std::io::stdin();
    let input = if false {
        algo_lib::io::input::Input::new_with_size(&mut sin, 1)
    } else {
        algo_lib::io::input::Input::new(&mut sin)
    };
    let mut stdout = std::io::stdout();
    let output = if false {
        algo_lib::io::output::Output::new_with_auto_flush(&mut stdout)
    } else {
        algo_lib::io::output::Output::new(&mut stdout)
    };
    solution::run(input, output);
}