#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
int n , m;
int a[3009];

void init()
{
    int u , v , w;
    for( int i = 1; i <= n; i++ ) a[i] = 0;
    for( int i = 1; i <= m; i++ )
    {
        scanf("%d%d%d",&u,&v,&w);
        if ( u == v ) continue;
        a[u] += w , a[v] += w;
    }
    int ans = 500000000;
    for( int i = 1; i <= n; i++ ) ans = min( ans , a[i] );
    printf("%d\n",ans);
}

int main()
{
    while( scanf("%d%d",&n,&m) == 2 )
    {
        init();
        //solve();
    }

    return 0;
}