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

int main(){
    int n, m;
    while(cin >> n >> m){
        int a[n+1];
        for(int i = 0; i < n+1; i++)
            a[i] = 0;
        while(m--){
            int u,v,w;
            cin >> u >> v >> w;
            if(u == v)
                continue;
            a[u] += w;
            a[v] += w;
        }
        sort(a+1, a+1+n);

        cout << a[1] << endl;
    }
}