#include <stdio.h>
#include <vector>
#define DIM 10000
char buff[DIM];
int poz=0;
 
void citeste(int &numar)
{
     numar = 0;
     //cat timp caracterul din buffer nu e cifra ignor      
     while (buff[poz] < '0' || buff[poz] > '9')     
          //daca am "golit" bufferul atunci il umplu
          if (++poz == DIM) 
               fread(buff,1,DIM,stdin),poz=0;
     //cat timp dau de o cifra recalculez numarul          
     while ('0'<=buff[poz] && buff[poz]<='9')
     {
          numar = numar*10 + buff[poz] - '0';
          if (++poz == DIM) 
               fread(buff,1,DIM,stdin),poz=0;               
     }     
}
std::vector<int> *adj,*cost;
int n,m,x,y;
bool ver[30001];
bool as=0;
void dfs(int sat,int counter)
{
     int a,b;
     ver[sat]=1;
     if(sat==y)
     {
               printf("%d\n",counter);
               as=1;
               return;
     }
     std::vector<int>::iterator it1,it2;
     for(it2=cost[sat].begin(),it1=adj[sat].begin();it1!=adj[sat].end();++it1,++it2)
     {
                                                        a=*it1;   
                                                        if(ver[a]==0)
                                                        {
                                                                        b=*it2;
                                                                        dfs(a,counter+b);
                                                                        if(as==1) return;
                                                        }
     }
     ver[sat]=0;
}
int main()
{
    freopen ("sate.in","r",stdin);
    freopen ("sate.out","w",stdout);
    citeste(n);
    citeste(m);
    citeste(x);
    citeste(y);
    int p1,p2,c;
    int temp;
    adj=new std::vector<int> [n+1];
    cost=new std::vector<int> [n+1];
    for(int i=1;i<=m;i++)
    {
            citeste(p1);
	    citeste(p2);
	    citeste(c);
            if(p1>p2)
            {
                     temp=p1;
                     p1=p2;
                     p2=temp;
            }
            adj[p1].push_back(p2);
            adj[p2].push_back(p1);
            cost[p1].push_back(c);
            c*=(-1);
            cost[p2].push_back(c);
    }
    dfs(x,0);
}