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Huhu_Miao: 2024-11-03 01:42:46
/**
 *    author:  Huhu_Miao
 *    created: 2024.11.3 01:41:00 (UTC+8)
**/
#include<bits/stdc++.h>

struct node
{
	bool exist;
	int in_degree;
};
void solve(){
	int n , m;
	std::cin >> n >> m;
	std::vector<std::vector<int>> succ(n,std::vector<int>(0));
	std::vector<node> nodes(n,{true,0});

	while(m--){
		int from , to;
		std::cin >> from >> to;
		nodes[to].in_degree++;
		succ[from].push_back(to);
	}

	bool zero_in_degree_node_exist = false;
	do{
		zero_in_degree_node_exist = false;
		for(int i = 0 ; i < n ; i++){
			if(nodes[i].in_degree == 0 && nodes[i].exist){
				zero_in_degree_node_exist = true;
				nodes[i].exist = false;
				for(int elem : succ[i]) nodes[elem].in_degree--;
				break;
			}
		}
	}while(zero_in_degree_node_exist);

	int ans = 0;
	for(auto node:nodes){
		if(node.in_degree == 0) ans++;
	}
	std::cout << ans << '\n';
}

int main(){
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);

	int T;
	std::cin>>T;

	while(T--){
		solve();
	}

	return 0;
}