#include<bits/stdc++.h>
using namespace std;
const int maxn=3e3+10;
int mp[maxn];
int main()
{
    ios::sync_with_stdio(false);
    int n,m,u,v,w,minl;
    while(cin>>n>>m)
    {
        minl=1<<30;
        memset(mp,0,sizeof(mp));
        for(int i=0;i<m;++i){
            cin>>u>>v>>w;
            if(v!=u){
                mp[v]+=w;
                mp[u]+=w;
            }
        }
        for(int i=1;i<=n;++i)
                minl=min(minl,mp[i]);
        cout<<minl<<endl;
    }
    return 0;
}