#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define ULL unsigned long long
#define Enter putchar('\n')
#define spc putchar(' ')
#define pb push_back
#define fi first
#define se second
inline void read(int &num){num=0;int f=1;char ch=getchar();while(ch>'9'||ch<'0'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){num=(num<<1)+(num<<3)+(ch^48);ch=getchar();}num*=f;}
inline void lread(long long &num){num=0;int f=1;char ch=getchar();while(ch>'9'||ch<'0'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){num=(num<<1)+(num<<3)+(ch^48);ch=getchar();}num*=f;}
void print(long long num){if(num<0){putchar('-');num=-num;}if(num>9){print(num/10);}putchar((num%10)^48);}
const int N=5e5+9;
LL a[N],b[N],g[N];
set<int> s;
int main(){
    int T,n;
    read(T);
    while(T--){
        read(n);
        LL s1=0,s2=0;
        for(int i=0;i<n;i++){
            lread(a[i]);
            s1+=a[i];
        }
        for(int i=0;i<n;i++){
            lread(b[i]);
            s2+=b[i];
        }
        if(s2>s1){
            for(int i=0;i<n;i++)swap(a[i],b[i]);
            swap(s2,s1);
        }
        b[0]+=s1-s2;
        s.clear();
        for(int i=1;i<n;i++)if(b[i])s.insert(i);
        int mi=1e9,p1,p2;
        for(int i=n-1;i;i--){
            if(!a[i])continue;
            auto it=s.lower_bound(n-i);
            if(it!=s.end()&&(*it)-n+i<=mi){
                mi=(*it)-n+i;
                p1=i,p2=(*it);
            }
        }
        if(mi==1e9){
            puts("0");
            continue;
        }
        --a[p1],--b[p2];
        LL ans=0,f=n-1;
        g[n-1]=b[n-1];
        for(int i=n-2;i>=0;i--){
            g[i]=g[i+1]+b[i];
        }
        for(int i=0;i<n;i++){
            ans+=min(a[i],g[n-i-1]-ans);
        }
        print(ans+1),Enter;
    }
    return 0;
}