#include<string>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
int m,n,l,i,j;
long long djsum[3005],mindj;
struct guanxi{
    int jl1;
    int jl2;
    int dj;
}a[100005];
int main()
{
    while(cin>>n>>m){
        memset(djsum,0,sizeof(djsum));    
        memset(a,0,sizeof(a));
        int mxi=0;
        for(int i=0;i<m;i++){
            cin>>a[i].jl1>>a[i].jl2>>a[i].dj;
            if(a[i].jl1!=a[i].jl2){
                djsum[a[i].jl1]+=a[i].dj;
                djsum[a[i].jl2]+=a[i].dj;
                if(a[i].jl1>mxi)mxi=a[i].jl1;
                if(a[i].jl2>mxi)mxi=a[i].jl2;    
            }
        }
            
        int count=0;mindj=djsum[1];
        for(i =1;i<=mxi;i++){
            if(djsum[i]!=0)count++;
            if(djsum[i]<mindj){
            mindj=djsum[i];
            }     
        }
        if(count!=n)cout<<"0"<<endl;
        else cout<<mindj<<endl;
    }    
    return 0;
}