#pragma warning(disable:4786)#include<stdio.h>#include<string.h>#include<string>#include<map>#include <set>#include<ctype.h>#include<algorithm>#include<map>#include<stack>#include<queue>#include<iostream>using namespace std;#include <math.h>int main(){int t;scanf("%d",&t);while(t--){int n,m;scanf("%d%d",&n,&m);stack<int> h[3];int i;int x,y;for(i=n;i>=1;i--){h[0].push(i);}int ans = 0;for(i=1;i<=m;i++){scanf("%d%d",&x,&y);x--,y--;if(h[x].empty()){ans = -1*i;break;}int tmp1 = h[x].top();h[x].pop();if(!h[y].empty()){int tmp2 = h[y].top();if(tmp1>tmp2){ans = -1*i;break;}h[y].push(tmp1);if(h[y].size()==n&&y==2){ans = i;break;}}else{h[y].push(tmp1);if(h[y].size()==n&&y==2){ans = i;break;}}}i++;for(;i<=m;i++){scanf("%d%d",&x,&y);}printf("%dn",ans);}return 0;}
