#include <iostream>
#include <string>
#include <queue>
#include <vector>
#include <algorithm>
#include <utility>
using namespace std;

/*
 * 6 <-- 11 -- 7
 * 7 <-- 19 -- 6
 *   -- -19 -> 6
 *
 */

bool topo(long long c, long long& temp, vector<vector<pair<long long, long long>>>& graph, vector<long long>& mark) {
	if (mark[c] == 2) return true;
	if (mark[c] == 1) return false;
	mark[c] = 1;
	for (pair<long long, long long>& p : graph[c]) {
		if (p.second < 0) continue;
		bool res = topo(p.first, temp, graph, mark);
		if (!res && temp < p.second) {
			mark[c] = 0;
			p.second *= -1;
			for (pair<long long, long long>& pa : graph[p.first]) {
				if (pa.first == c) {
					pa.second *= -1;
					break;
				}
			}
			res = topo(p.first, temp, graph, mark);
			if (!res) return false;
		}
	}
	mark[c] = 2;
	return true;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);

	long long N, M;
	cin >> N >> M;
	vector<vector<pair<long long, long long>>> graph(N+1, vector<pair<long long, long long>>());
	for (long long i = 0; i < M; i++) {
		long long ai, bi, ci;
		cin >> ai >> bi >> ci;
		graph[bi].push_back({ ai, ci });
		graph[ai].push_back({ -bi, ci });
	}
	for (long long t = 0; t < 20; t++) {
		vector<long long> mark(N+1);
		if (topo(1, t, graph, mark)) {
			cout << t << endl;
		}
	}
}