#include<cstdio>
#include<cstring>
#include<algorithm>
#include<utility>
#include<ctime>
#include<vector>
#include<queue>
#include<iostream>
#include<set>
#include<random>
#include<cassert>
#include<string>
#include<cmath>
#include<bitset>
#include<chrono>
#include<map>
#include<unordered_map>
#define eb emplace_back

using namespace std;
const int maxn=5e5+10, maxm=1.2e4+10, inf=2e9+12;
typedef long long LL;
typedef unsigned long long ULL;
const LL INF=4e18;
typedef pair<int, int> pii;
typedef pair<LL, int> pli;
typedef pair<int, LL> pil;

inline int read() {
    int x=0, f=1; char c=getchar();
    for(; c<'0'||c>'9'; c=getchar()) if(c=='-') f=0;
    for(; c>='0'&&c<='9'; c=getchar()) x=x*10+c-'0';
    return f?x:-x;
}
int P=1e9;
inline int add(int x, int y) {x+=y; return x>=P?x-P:x;}
inline int del(int x, int y) {x-=y; return x<0?x+P:x;}
inline int ksm(int x, int y) {
    int s=1; for(; y; y>>=1, x=1LL*x*x%P) if(y&1) s=1LL*s*x%P; return s;
}
mt19937 rnd((unsigned)chrono::steady_clock::now().time_since_epoch().count());
int gcd(int x, int y) {return y?gcd(y, x%y):x;}


LL a[maxn], b[maxn];
int main() {
    int T=read();
    while(T--) {
        int m=read();
        LL suma=0, sumb=0;
        for(int i=0; i<m; ++i) a[i]=read(), suma+=a[i];
        for(int i=0; i<m; ++i) b[i]=read(), sumb+=b[i];
        if(suma<sumb) a[0]+=sumb-suma; else b[0]+=suma-sumb;
        int mxa=0, mxb=0;
        for(int i=0; i<m; ++i) if(a[i]>0) mxa=i;
        for(int i=0; i<m; ++i) if(b[i]>0) mxb=i;
        if(mxa+mxb<m) {printf("0\n"); continue;}
        LL c=0; int t=m-1, fl=0, mna=1e9, mnb=1e9;
        for(int i=0; i<m; ++i) {
            while(t>=m-i-1) {
                LL tmp=min(a[i], b[t]);
                if(tmp>0) {
                    if(i+t>=m) fl=1;
                    mna=min(mna, i);
                    mnb=min(mnb, t);
                }
                c+=tmp; a[i]-=tmp; b[t]-=tmp;
                if(b[t]==0) --t;
                if(a[i]==0) break;
            }
        }
        if(fl) printf("%lld\n", c);
            else printf("%lld\n", c-1);

    }
    return 0;
}