#include <bits/stdc++.h>
using namespace std;
using ll = long long;

// red, blue
bool dfs(ll v, pair<ll,ll> sum, vector<bool>& seen, vector<pair<ll,ll>>& sums, const vector<vector<pair<ll,ll>>>& heig){
    seen[v] = true;

    for (auto&& [dest, c]: heig[v]) {
        auto [cr,cb]{sum};
sums[v] = {cr,cb};

if (c == 0){
            ++cr;
        } else{
            ++cb;
        }
         if (seen[dest]) {
                auto [r,b]{sums[dest]};
                auto [cr,cb]{sum};

                if (cr - r == 1 || cb - b == 1){
                    return false;
                }
            }
            else {
                auto r = dfs(dest, {cr,cb}, seen, sums, heig);
                if (!r){
                    return false;
                }
            }
        }

    return true;
}




int main(){
    ll n,m;
    cin >> n >> m;
    // dest , colour
    vector<vector<pair<ll,ll>>> heighbors(n,vector<pair<ll,ll>>());

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

        heighbors[u].emplace_back(v,c);
        heighbors[v].emplace_back(u,c);
    }

    vector<bool> seen(n, false);
    vector<pair<ll,ll>> sums(n, pair<ll,ll>(0,0));
    if (dfs(0, {0,0}, seen, sums, heighbors)){
        cout << "YES" << endl;
    }
    else {
        cout << "NO" << endl;
    }
     return 0;
}