//solutia cu dijkstra
#include <iostream>
#include <cstdio>

using namespace std;

const char iname[] = "pscnv.in";
const char oname[] = "pscnv.out";
const int  nmax    = 250005;
const int  infinite= 2188989;

int n, m, a1, a2, x, y, c, i, j;
int father[nmax];
int len[nmax];

struct muchie
{
	int nod1;
	int nod2;
}muchii[1005][10000];

int find(int nod)
{
	if(father[nod] == nod)
		return nod;
	father[nod] = find(father[nod]);
	return father[nod];
}

void unite(int x, int y)
{
	int f1 = find(x);
	
	int f2 = find(y);
	father[f1] = f2;
}

int main()
{	
	
	freopen(iname, "r", stdin);
	freopen(oname, "w", stdout);
	scanf("%d %d %d %d", &n, &m, &a1, &a2);
	for(i = 1; i <= m; i ++)
	{
		scanf("%d %d %d", &x, &y, &c);
		muchii[c][++len[c]].nod1 = x;
		muchii[c][len[c]].nod2 = y;
	}
		
	a1 = 1, a2 = n;
	for(i = 1; i <= n; i ++)
		father[i] = i;
	
	for(i = 1; i <= 1005; i ++)
		for(j = 1; j <= len[i]; j ++)
		{	
			if(father[muchii[i][j].nod1] != father[muchii[i][j].nod2])
				unite(find(muchii[i][j].nod1), find(muchii[i][j].nod2));
			if(find(a1) == find(a2))
			{
				printf("%d", i);
				return 0;
			}
		}
	

	return 0;
}