#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9;
int N, M;
int L[100005];
int R[100005];
int val[100005];
array<int, 3> A[100005];
struct SegTree {
struct Node {
int mi, p;
Node():mi(0), p(0) {}
Node(int _m, int _p) : mi(_m), p(_p) {}
};
vector<Node> seg;
int MAX;
SegTree(int N) {
int i;
for(i=1;i<2*N;i*=2) {}
seg.resize(i);
MAX = i;
}
void cons() {
for(int i = MAX/2-1;i>=1;i--) {
seg[i].mi = min(seg[2*i].mi, seg[2*i+1].mi);
}
}
void prop(int n, int ns, int ne) {
if(seg[n].p) {
seg[n].mi += seg[n].p;
if(n < MAX/2) {
seg[2*n].p += seg[n].p;
seg[2*n+1].p += seg[n].p;
}
seg[n].p = 0;
}
}
void add(int s, int e, int k, int n, int ns, int ne) {
prop(n,ns,ne);
if(e<=ns||ne<=s) return;
if(s<=ns&&ne<=e) {
seg[n].p += k;
prop(n,ns,ne);
return;
}
int mid = ns + ne >> 1;
add(s, e, k, 2*n, ns, mid);
add(s, e, k, 2*n+1, mid, ne);
if(n<MAX/2) seg[n].mi = min(seg[2*n].mi, seg[2*n+1].mi);
}
int sum(int s, int e, int n, int ns, int ne) {
prop(n,ns,ne);
if(e<=ns||ne<=s) return INF;
if(s<=ns&&ne<=e) return seg[n].mi;
int mid = ns + ne >> 1;
return min(sum(s, e, 2*n, ns, mid), sum(s, e, 2*n+1, mid, ne));
}
};
bool isPos(int c) {
//cout << "isPos " << c << '\n';
int i, j;
for(i=0;i<M;i++) val[i] = -1;
for(i=0;i<N;i++) L[i] = M, R[i] = -1;
for(i=0;i<c;i++) {
if(val[A[i][0]]==-1) val[A[i][0]] = A[i][2];
else if(val[A[i][0]] != A[i][2]) return false;
L[A[i][1]] = min(L[A[i][1]], A[i][0]);
R[A[i][1]] = max(R[A[i][1]], A[i][0]);
}
//cout << "step 1\n";
priority_queue<array<int, 2>, vector<array<int, 2>>, greater<array<int, 2>>> PQ1, PQ2;
int free = 0;
for(i=0;i<N;i++) {
if(R[i]==-1) free++;
else PQ1.push({L[i], i});
}
/*for(i=0;i<M;i++) {
cout << val[i] << ' ';
}
cout << '\n';*/
int m = 0;
int must = 0;
SegTree tree(M+3);
int MAX = tree.MAX;
for(i=0;i<M;i++) {
int v = (val[i] == -1 ? INF : val[i]);
tree.seg[i+MAX/2].mi = v;
}
tree.cons();
for(i=0;i<N;i++) {
if(R[i]!=-1) {
tree.add(L[i], R[i]+1, -1, 1, 0, MAX/2);
}
}
for(i=0;i<M;i++) {
//cout << i << " : " << val[i] << '\n';
if(val[i] == -1) continue;
while(!PQ1.empty() && PQ1.top()[0] <= i) {
auto k = PQ1.top();
PQ1.pop();
PQ2.push({R[k[1]], k[1]});
must++;
m++;
}
//cout << m << ' ' << must << ' ' << free << '\n';
if(m >= val[i]) {
m = min(m, val[i]);
if(m < must) return false;
}
else {
while(!PQ1.empty() && m < val[i]) {
auto k = PQ1.top();
int id = k[1];
int v = tree.sum(i, L[id], 1, 0, MAX/2);
if(v <= 0) break;
else {
PQ1.pop();
PQ2.push({R[id], id});
tree.add(i, L[id], -1, 1, 0, MAX/2);
must++;
m++;
}
}
if(m < val[i]) {
free -= val[i] - m;
m = val[i];
if(free < 0) return false;
}
}
while(!PQ2.empty() && PQ2.top()[0] <= i) {
PQ2.pop();
must--;
}
}
return true;
}
void solve() {
cin >> N >> M;
int i, j;
for(i=0;i<M;i++) {
int a, b, c;
cin >> a >> b >> c;
a--, b--;
A[i] = {a, b, c+1};
}
int s = 0, e = M;
while(s+1<e) {
int mid = (s+e)/2;
if(isPos(mid+1)) s = mid;
else e = mid;
}
cout << s+1 << '\n';
}
signed main() {
cin.sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int t;
cin >> t;
while(t--) {
solve();
}
}
