1 #include <bits/stdc++.h>
 2 #define pb push_back
 3 #define _for(i,a,b) for(int i = (a);i < (b);i ++)
 4 #define INF INT_MAX
 5 #define ll long long
 6 
 7 using namespace std;
 8 
 9 const int maxn = 500003;
10 inline ll read()
11 {
12     ll ans = 0;
13     char ch = getchar(), last = ' ';
14     while(!isdigit(ch)) last = ch, ch = getchar();
15     while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
16     if(last == '-') ans = -ans;
17     return ans;
18 }
19 inline void write(ll x)
20 {
21     if(x < 0) x = -x, putchar('-');
22     if(x >= 10) write(x / 10);
23     putchar(x % 10 + '0');
24 }
25 struct edge
26 {
27     ll to;
28     ll cost;
29 };
30 vector<edge> G[maxn];
31 
32 ll V,E;
33 
34 typedef pair<ll,ll> P;//first 是最短距离，second 是顶点编号 
35 ll d[maxn];
36 void shortest_path(ll s)
37 {
38     priority_queue<P,vector<P>,greater<P>> que;
39     
40     _for(i,1,V+1)
41         d[i] = INF;
42     d[s] = 0;
43     que.push(P{0,s});
44 
45     while(!que.empty())
46     {
47         P p = que.top();que.pop();
48         ll v = p.second;
49         if(d[v] < p.first) continue;
50         _for(i,0,G[v].size())
51         {
52             edge e = G[v][i];
53             if(d[e.to] > d[v] + e.cost)
54             {
55                 d[e.to] = d[v] + e.cost;
56                 que.push(P{d[e.to],e.to});
57             }
58         }
59     }
60 }
61 
62 int main()
63 {
64     ll st,ed;
65     V = read(),E = read(),st = read(),ed = read();
66 //    scanf("%d %d %d",&V,&E,&st);
67     _for(i,0,E)
68     {
69         ll s,t,c;
70         s = read(),t = read(),c = read();
71         //  scanf("%d %d %d",&s,&t,&c);
72         G[s].push_back(edge {t,c});
73          G[t].push_back(edge{s,c});
74     }
75     shortest_path(st);
76     write(d[ed]);
77     //printf("%d ",d[i]);
78     return 0;
79 }