Untitled

#include <bits/stdc++.h>
using namespace std ;
#define ll long long
#define For(n) for(long long i = 0; i < n; i++)
#define endl '\n'
#define int long long
struct node {
    int id;
    int score;    
};
struct cmp{
    bool operator() (node n1,node n2)const{
        if(n1.score<n2.score)return 1;
        else if(n1.score>n2.score)return 0;
        else return n1.id>n2.id;        
    } 
};
void solve(){
    map<int,int> mp;
    int n,q,x,y;;cin>>n>>q;
    set<node,cmp>prevscores;
    cin>>x>>y;mp[x]+=y;
    int ans=0,mxscore = y,winnerteam=x;
    for(int i=1;i<q;i++){
       cin>>x>>y;
        mp[x]+= y;
        if(x==winnerteam && mp[x]<mxscore){// if winner team got fuckedup  
            mxscore = mp[x];// update mxscore         
            if(prevscores.empty())continue;       
            node curr = *prevscores.crbegin();                
            if(mxscore<curr.score){
                ans = i;
                mxscore = curr.score;
                winnerteam = curr.id;
                prevscores.erase(curr);                
            }
            else if(mxscore==curr.score){
                if(x>curr.id){
                    ans = i;
                    winnerteam =curr.id;   
                    prevscores.erase(curr);             
                }               
            }
        }
        else if(mp[x]>mxscore){            
            if(winnerteam!=x){
                ans = i;
                node neww; neww.id=winnerteam,neww.score=mxscore;
                prevscores.insert(neww);
            }
            winnerteam = x; 
            mxscore = mp[x];
        }
        else if(mp[x] == mxscore){
            if(x<winnerteam){
                ans = i;
                node neww;neww.id=winnerteam,neww.score=mxscore;
                prevscores.insert(neww);                
                winnerteam = x;
            }
            else{
                node neww,old;
                neww.id=x,neww.score=mp[x];
                old.id =x;old.score = mp[x]-y;
                if(prevscores.find(old)!=prevscores.end()) prevscores.erase(old);
                prevscores.insert(neww);                
            }
        }
            else{
                node neww,old;
                neww.id=x,neww.score=mp[x];
                old.id =x,old.score = mp[x]-y;
                if(prevscores.find(old)!=prevscores.end()) prevscores.erase(old);
                prevscores.insert(neww);                
            }
        // cout << winnerteam<<' '<<mxscore<<' '<<prevscores.top().id<<' '<<prevscores.top().score<<endl;
    }
    if(ans)ans++;
    cout << ans << endl;
}

signed main ()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);    
int t =1;
cin>>t;
while (t--){
    solve();
}    
}