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

int main() {
    int n, m;
    if (scanf("%d %d", &n, &m) != 2) return 0;

    vector<long long> d(n + 1, 0);
    for (int i = 0; i < m; i++) {
        int u, v;
        long long w;
        scanf("%d %d %lld", &u, &v, &w);
        d[u] += w;
        d[v] += w;
    }

    vector<long long> a(d.begin() + 1, d.end());
    sort(a.begin(), a.end(), greater<long long>());

    long long s = 0;
    for (int i = 0; i < n; i++) {
        if (i % 2 == 0) s += a[i];   // Alice
        else            s -= a[i];   // Bob
    }
    printf("%lld\n", s / 2);
    return 0;
}