#include<iostream>

#include<cstring>

#include<cstdio>

#include<set>

using namespace std;

#define N 100005

int s[N],win[N];

struct Node {

    int id,sc;

    Node(int i=,int s=) {

        id = i;

        sc = s;

    }

    bool operator < (Node A) const {

        if(A.sc != sc) return sc > A.sc;

        else return id < A.id;

    }

};

set<Node> st;

set<Node>::iterator it;

int main() {

//    freopen("C.in.cpp","r",stdin);

    int T,n,q,x,p;

    scanf("%d",&T);

    while(T--) {

        st.clear();

        memset(s,,sizeof(s));

        scanf("%d%d",&n,&q);

        for(int i = ; i <= n; i++) {

            st.insert(Node(i,));

        }

        win[] = ;

        for(int i = ; i <= q; i++) {

            scanf("%d%d",&x,&p);

            st.erase(Node(x,s[x]));

            s[x] += p;

            st.insert(Node(x,s[x]));

            it = st.begin();

            Node tmp = *it;

            win[i] = (*it).id;

        }

        int i;

        for(i = q; i >= ; i--) {

            if(win[i] != win[i-]) {

                break;

            }

        }

        printf("%d\n",i);

    }

    return ;

}