#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
#include <algorithm>
using namespace std;
const int N = 2510,M =12410;
typedef pair<int,int> PII;
int h[N],e[M],ne[M],w[M],idx;
int n,m,s,E;
int dist[N];
bool st[N];
void add(int a,int b,int c)
{
e[idx] = b,w[idx] = c,ne[idx] = h[a],h[a] = idx++;
}
void dijkstra()
{
memset(dist,0x3f,sizeof(dist));
dist[s] = 0;
priority_queue<PII,vector<PII>,greater<PII>> heap;
heap.push({0,s});
while(heap.size())
{
auto t = heap.top();
heap.pop();
int ver = t.second,distance = t.first;
if(st[ver])continue;
st[ver] = true;
for(int i = h[ver];i != -1;i = ne[i])
{
int j = e[i];
if(dist[j] > distance + w[i])dist[j] = distance + w[i];
heap.push({dist[j],j});
}
}
printf("%d\n",dist[E]);
}
int main()
{
scanf("%d%d%d%d",&n,&m,&s,&E);
memset(h,-1,sizeof(h));
while(m--)
{
int a,b,c;
scanf("%d%d%d",&a,&b,&c);
add(a,b,c),add(b,a,c);
}
dijkstra();
return 0;
}