#include "bits/stdc++.h"
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
using namespace std;
#define int long long

const int N= 1e3 + 10;
int dp[N][N][15];
int a[N], b[N];
int mnTime[N][N], n;
//mnTime[i][j]: the minimum required amount of time for baudi to start at i, ends at j

int memo[N];
int solve(int i, int j, int spent){
         if(j > n){
                  return INT_MAX;
         }
         int &ret= dp[i][j][spent];
         if(ret != -1) return ret;

         //andi wants to read book i
         //baudi is reading book j and has spent [spent] hours reading it
         if(j == n)
         {
                  int sum = 0;
                  for(int k = i; k < n; k++)
                           sum += a[i];
                  return ret= sum;
         }

         ret= INT_MAX;
         if(i == j)
         {
                  if (spent == b[j]){
                           ret= solve(i, j + 1, 0);
                           if(j + 1 != n - 1) ret= min(ret, solve(i, j + 2, 0));
                           return ret;
                  }
                  return ret = solve(i, j, spent + 1) + 1;
         }

         if(a[i] < b[j] - spent)
         {
                  //he will finish reading it before me
                  return ret= a[i] + solve(i + 1, j, min(b[j], spent + a[i]));
         }

         int L = j, R= n - 1, best= j;
         while(L <= R)
         {
                  int md= (L + R) / 2;
                  if(mnTime[j][md] - spent <= a[i])
                           best= md, L= md + 1;
                  else
                           R= md - 1;
         }



         for(int to = best - 50; to < best + 50; to++)
         {
                  if(to < j || to > n - 1)
                           continue;

                  if(mnTime[j][to] - spent <= a[i])
                  {
                           int rem= a[i] - mnTime[j][to] + spent;
                           int ch= solve(i + 1, to + 1, min(b[to + 1], rem));
                           if(to + 1 != n - 1) {
                                    //we can skip it
                                    ch= min(ch, solve(i + 1, to + 2, min(b[to + 2], rem)));
                           }
                           ret= min(ret, a[i] + ch);
                  }
         }
         return ret;
}
int32_t main(){
         cin.tie(0);
         cin.sync_with_stdio(0);

         cin>>n;
         for(int i = 0; i < n; i++){
                  cin>>a[i];
         }
         for(int i = 0; i < n; i++){
                  cin>>b[i];
         }
         for(int ed = n - 1; ed >= 0; ed--)
         {
                  memo[ed]= b[ed];
                  mnTime[ed][ed]= b[ed];
                  memo[ed + 1]= INT_MAX;
                  for(int i = ed - 1; i >= 0; i--){
                           memo[i]= b[i] + min(memo[i + 1], memo[i + 2]);
                           mnTime[i][ed]= memo[i];
                  }
         }
         memset(dp, -1, sizeof dp);
         cout<<solve(0, 0, 0)<<"\n";
}