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#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;
}
}
}
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