#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N, M; cin>>N>>M;
    vector<ll> com(N+1, 0);
    for (int i=0;i<M;i++){
        int U, V; ll W; cin>>U>>V>>W;
        com[U]+=W;
        com[V]+=W;
    }
    sort(&com[1], &com[N+1], greater<ll>());

    ll a=0, b=0;
    for (int i=1;i<=N;i++){
        if (i%2==1) a+=com[i];
        else b+=com[i];
    }
    cout << (a-b)/2 << "\n";
    return 0;
}