#include <bits/stdc++.h>

using namespace std;

#define sz(x) (int)x.size()

using ll = long long;
using ull = unsigned long long;

signed main() {
    int n, m;

    cin >> n >> m;

    using Edge = struct {
        int next, blue;
    };
    vector<vector<Edge>> g(n);

    int u, v, blue;
    for (int i = 0; i < m; i++) {
        cin >> u >> v >> blue;

        g[u].push_back(Edge(v, blue));
        g[v].push_back(Edge(v, blue));
    }

    vector<bool> vis(n, false);

    for (int i = 0; i < n; i++) {
        if (vis[i]) continue;

        vis[i] = true;
        vector<int> q;
        q.push_back(i);
        for (int j = 0; j < sz(g[i]); j++) {
            if (vis[g[i][j].next]) continue;
            vis[g[i][j].next] = true;
        int pivot = g[i][j].blue;

            while (!q.empty()) {
                int cur = q.back();
                q.pop_back();

                for (int i = 0; i < sz(g[cur]); i++) {
                    if (g[cur][i].blue != pivot) {
                        cout << "NO" << '\n';
                        return 0;
                    }
                    if (vis[g[cur][i].next]) continue;
                    vis[g[cur][i].next] = true;
                    q.push_back(g[cur][i].next);
                }
            }
        }


    }


    cout << "YES" << '\n';
    return 0;
}