#include <cstring>
#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

int N, M, X, Y, K, Kmax;
vector<pair<int, int> > V[250002];
bool S[250002];
int testnow;

void Dfs(int A)
{
    S[A] = true;
    for (vector<pair<int, int> >::iterator it = V[A].begin(); it != V[A].end(); ++it)
        if (it->second <= testnow && !S[it->first])
            Dfs(it->first);
}
bool Test(int value)
{
    testnow = value;
    memset(S, 0, sizeof(S));
    Dfs(X);
    return S[Y];
}

int main()
{
    ifstream fin("pscnv.in");
    ofstream fout("pscnv.out");

    fin >> N >> M >> X >> Y;
    for (int i = 1, nod1, nod2, cost; i <= M; ++i)
    {
        fin >> nod1 >> nod2 >> cost;
        V[nod1].push_back(make_pair(nod2, cost));
        Kmax = max(Kmax, cost);
    }

    int step;
    for (step = 1; (step << 1) <= Kmax; step <<= 1);
    for (K = Kmax + 1; step; step >>= 1)
        if (K - step >= 1 && Test(K - step))
            K -= step;

    fout << K;

    fin.close();
    fout.close();
}