#include <cstdio>
#include <vector>
#include <algorithm>

const int maxK = 1010;
const int maxN = 250100;

using namespace std;

vector < pair <int, int> > T[maxK];
int N, M, x, y;
vector <int> G[maxN];
int P[maxN];

inline int tata(int x) {
	if (x == P[x])
		return x;
	P[x] = tata(P[x]);
	return P[x];
}

int main() {
	int i, j, a, b, c;
	freopen("pscnv.in", "r", stdin);
	freopen("pscnv.out", "w", stdout);

	scanf("%d%d%d%d", &N, &M, &x, &y);
	for (i = 1; i <= M; i++) {
		scanf("%d%d%d", &a, &b, &c);
		T[c].push_back(make_pair(a, b));
	}

	for (i = 1; i <= N; i++)
		P[i] = i;

	for (i = 1; i <= 1000; i++) {
		for (j = 0; j < T[i].size(); j++) {
			if (tata(T[i][j].first) != tata(T[i][j].second)) 
				P[tata(T[i][j].first)] = tata(T[i][j].second);
		}

		if (tata(x) == tata(y)) {
			printf("%d\n", i);
			return 0;
		}
	}



	return 0;
}