#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

ll n,m;
ll c[100009],a[100009];

void solve(){
    cin>>n>>m;
    ll sumc=0;
    for(ll i=1;i<=n;i++) {cin>>c[i];a[i]=c[i];sumc+=c[i];}
    ll ans=-1;
    ll dr=0;
    ll lstx=0; 
    for(ll i=1;i<=m;i++){
      //  cout<<lstx<<'\n';
        ll x,t;
        cin>>x>>t;
        if(ans>=0) continue;
        dr+=x-lstx;
        if(dr>sumc){
            ans=x-(dr-sumc);
        }
        if(dr<c[t]) dr=0;
        else dr-=c[t];
        lstx=x;
    }
    if(ans==-1) ans=lstx+sumc-dr;
    cout<<ans<<'\n';
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    int n=1;
    cin>>n;
    while(n--)solve();
    return 0;
}