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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int N, M;
    cin >> N >> M;
    
    vector<tuple<long long,int,int>> edges(M);
    for(auto& [w,u,v] : edges){
        cin >> u >> v >> w;
    }
    
    // Sort edges by weight descending
    sort(edges.begin(), edges.end(), greater<>());
    
    long long score = 0;
    for(int i = 0; i < M; i++){
        auto [w,u,v] = edges[i];
        if(i % 2 == 0) score += w;  // Alice's turn -> +W
        else score -= w;             // Bob's turn -> -W
    }
    
    cout << score << "\n";
    return 0;
}