#include <cstdio>
#include <vector>
#include <cstring>
#define dim 8192 
using namespace std;
const char iname[] = "pscnv.in";
const char oname[] = "pscnv.out";
struct nod{
	int y, c; nod(){}; nod(int m, int n){ y = m; c = n;};
};
vector <nod> v[250004];
bool viz[250004];
int x;
char ax[dim];
int pz;
inline void cit(int &x){
    x = 0;
    while (ax[pz] < '0' || ax[pz] > '9')
        if (++pz == dim)
            fread (ax, 1, dim, stdin), pz = 0;
    while (ax[pz] >= '0' && ax[pz] <= '9'){
        x = x * 10 + ax[pz] - '0';
        if (++pz == dim)
            fread (ax, 1, dim, stdin), pz = 0;
    }
}
int N, M, A, B, i, j, g, h, mv, ANS;
inline void DFS(int node, int X)
{
	vector <nod> :: iterator it, fin;
	viz[node] = true;
	it = v[node].begin();
	fin = v[node].end();
	for (; it != fin; ++it)
	{
		if (!viz[it -> y] && it -> c <= X) 
			DFS(it -> y, X); 
	}
}
inline int BS(){
	int Mij, St = 1, Dr = mv;
	while (St <= Dr){
		Mij = (St + Dr) / 2;
		DFS(A, Mij);
		if (!viz[B]) St = Mij + 1;
		else{
			Dr = Mij - 1;
			ANS = Mij;
		}
		memset(viz, 0, sizeof(viz));
	}
	return ANS;
}
int main()
{
	freopen(iname,"r",stdin);
	freopen(oname,"w",stdout);
	scanf("%d%d%d%d", &N, &M, &A, &B);
	//cit(N); cit(M); cit(A); cit(B);
	/*
	while (M--){
        cit(g); cit(h); cit(i);
		if (i > mv) mv = i;
        v[g].push_back(nod(h, i));
    }
	*/
	while (M--){
        scanf("%d%d%d", &g, &h, &i);
		if (i > mv) mv = i;
        v[g].push_back(nod(h, i));
    }
	printf("%d\n", BS());
	return 0;
}