#include <stdio.h>   
#include <vector>   
using namespace std;   
  
#define NMAX 250010   
  
int N, M, beg, end;   
  
vector <pair<int, int> > leg[1010];   
  
int tata[NMAX];   
  
int unite(int x, int y)   
{   
    if (rand() & 1) tata[x] = y;   
    else tata[y] = x;   
}   
  
int father(int x)   
{   
    if (tata[x] == x) return x;   
    return tata[x] = father(tata[x]);   
}   
  
int bg;   
char s[100];   
  
void GET(int &x)   
{   
    for (; s[bg] && !('0' <= s[bg] && s[bg] <= '9'); bg++);   
       
    for (x = 0; '0' <= s[bg] && s[bg] <= '9'; bg++)   
        x = x * 10 + s[bg] - '0';   
}   
  
int main()   
{   
    int i, x, y, c;   
       
    freopen("pscnv.in", "r", stdin);   
    freopen("pscnv.out", "w", stdout);   
       
    scanf("%d %d %d %d\n", &N, &M, &beg, &end);   
       
    for (i = 1; i <= N; i++) tata[i] = i;   
       
    for (i = 1; i <= M; i++) {   
//      fgets(s, 100, stdin); bg = 0;   
//      GET(x); GET(y); GET(c);   
        scanf("%d %d %d", &x, &y, &c);   
           
        leg[c].push_back(make_pair(x, y));   
    }   
       
    for (i = 1; i <= 1000; i++) {   
        for (vector <pair<int, int> > :: iterator it = leg[i].begin(); it != leg[i].end(); ++it) {   
            x = father(it->first); y = father(it->second);   
            if (x != y) unite(x, y);   
        }   
  
               
        if (father(beg) == father(end)) break;   
    }   
       
    printf("%d\n", i);   
       
return 0;   
}