#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn=1e5+10;
int main()
{
    int i,n,m,u,v,w,a[maxn];
    while(cin>>n>>m)
    {
        memset(a,0,sizeof(a));
        while(m--)
        {
            cin>>u>>v>>w;
            if(u==v)
                continue;
            a[u]+=w;
            a[v]+=w;
        }
        sort(a+1,a+n+1);
        cout<<a[1]<<endl;
    }
    return 0;
}