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#include<bits/stdc++.h>
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using namespace std;
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const int N=4e4+10;
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int n,m,st,ed,head[N],f[N][510],u,v,sx,sy,sz,fx,fy,fz,cnt,x,y,z,ma=INT_MIN,mi=INT_MAX;
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struct Node{int x,y;};
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queue<Node>q;
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struct Edge{int to,nxt,val;}E[N<<1];
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void add(int x,int y,int z){E[++cnt]={y,head[x],z};head[x]=cnt;}
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namespace FastIO {
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 char *p1, *p2, buf[1 << 14];
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 #define getchar() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, (1 << 14), stdin), p1 == p2) ? EOF : *p1++)
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 template <typename T>
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 inline void read(T& x) {
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     x = 0;
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     register int t = 1;
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     register char ch = getchar();
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     while (ch < '0' || ch > '9') {
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         if (ch == '-')
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             t = -1;
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         ch = getchar();
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     }
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     while (ch >= '0' && ch <= '9'){
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         x = (x << 1) + (x << 3) + (ch ^ 48);
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         ch = getchar();
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     }
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     x *= t;
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 }
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 template <typename T>
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 void write(T x) {
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     if (x < 0) {
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         putchar('-');
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         x = -x;
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     }
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     if (x > 9) write(x / 10);
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     putchar(x % 10 ^ 48);
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 }
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 template <typename T>
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 inline void writeln(T x, char sep = '\n') {
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  write(x);
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  putchar(sep);
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 }
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}
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using namespace FastIO;
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int main(){
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 read(n);read(m);read(st);read(ed);
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 for(register int i=1;i<=m;++i){
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  read(x),read(y),read(z);
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  add(x,y,z),add(y,x,z),ma=(z>ma)?z:ma;
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 }
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 if(ma<=1){
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  for(register int i=head[ed];i;i=E[i].nxt)if(!E[i].val)return cout<<0,0;
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  return cout<<1,0;
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 }
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 q.push({ed,1});
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 while(!q.empty()){
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 register int u=q.front().x,fy=q.front().y,fz=f[u][fy-1];q.pop();
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  if(fy>=482)break;
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  for(register int i=head[u];i;i=E[i].nxt){
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   register int v=E[i].to,sx=fz+E[i].val/fy,sy=fy+1;
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   if(f[v][fy]<=sx&&f[v][fy])continue;
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   q.push({v,sy});f[v][fy]=sx;
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  }
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 }
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 for(register int i=0;i<=482;++i)if(f[st][i])mi=(f[st][i]<mi)?f[st][i]:mi;
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 cout<<mi;
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}