#include<iostream>
#include<cstdio>
#include<algorithm>
#define int long long
using namespace std;
const int MX=500050;
const int inf=1e15;

int T, N;
int ar[MX], br[MX];
int read()
{
    int r=0, f=1; char ch=getchar();
    while(ch<'0'||ch>'9') {if(ch=='-') f=-1; ch=getchar();}
    while(ch>='0'&&ch<='9') {r=r*10+ch-'0'; ch=getchar();}
    return r*f;
}
signed main()
{
    // freopen("testdata.in","r",stdin);
    T=read();
    while(T--)
    {
        N=read();
        int sa=0, sb=0;
        for(int i=0;i<N;i++) ar[i]=read(), sa+=ar[i];
        for(int i=0;i<N;i++) br[i]=read(), sb+=br[i];
        if(sa<sb) ar[0]+=sb-sa;
        else br[0]+=sa-sb;
        int suf=0, tag=1, ans=0;
        for(int i=0;i<N;i++)
        {
            suf+=br[N-i-1];
            // cout << ar[i] << " " << suf << '\n';
            int num=min(ar[i],suf);
            ans+=num, suf-=num;
            // cout << "suf=" << suf << '\n';
            if(suf&&i!=N-1) tag=0;
            // cout << "i=" << i << ", ans=" << ans << '\n';
        }
        if(!ans) cout << "0\n";
        else cout << ans-tag << '\n';
    }
    return (0-0);
}