#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
struct edge {
    int a, b, cost;
};

int n, m;
vector<edge> e;
const int INF = 1000000000;

void solve() {
    vector<int> d (n);
    vector<int> p (n, -1);
    int x;
    for (int i=0; i<n; ++i) {
        x = -1;
        for (int j=0; j<m; ++j)
            if (d[e[j].b] > d[e[j].a] + e[j].cost) {
                d[e[j].b] = max (-INF, d[e[j].a] + e[j].cost);
                p[e[j].b] = e[j].a;
                x = e[j].b;
            }
    }

    if (x == -1)
        cout << "NO";
    else {
        int y = x;
        for (int i=0; i<n; ++i)
            y = p[y];

        vector<int> path;
        for (int cur=y; ; cur=p[cur]) {
            path.push_back (cur);
            if (cur == y && path.size() > 1)  break;
        }
        //reverse (path.begin(), path.end());
        int min_ = n + 2;
        for (auto i : path) {
            if (min_ > i) min_ = i;
        }
        cout << "YES" << endl << min_;
    }
}
int main() {
    cin >> n >> m;
    e.resize(m);
    for (int i = 0; i < m; ++i) {
        cin >> e[i].a >> e[i].b >> e[i].cost;
    }
    solve();
    return 0;
}