#include<bits/stdc++.h>
using namespace std;
#define int long long
void solve(){
    int n,m;
    int o,x;
    set<int>fir,sec;
    cin>>n>>m;
    bool b=0;
    for(int i=1;i<=m;i++){
        cin>>o>>x;
        if(fir.count(x)+sec.count(x)==2||fir.size()==n||sec.size()>=2){
            if(!b)cout<<i-1<<endl;
            b=1;
            continue;
        }
        if(o==1)fir.insert(x);
        else sec.insert(x);
    }
    if(fir.count(x)+sec.count(x)==2||fir.size()==n||sec.size()>=2){
        if(!b)cout<<m<<endl;
        b=1;
        //continue;
    }
    else{
        if(b==0)cout<<"-1"<<endl;
    }
}
signed main(){
    int T;
    cin>>T;
    for(int i=1;i<=T;i++){
        solve();
    }
}