#include <fstream>
#include <vector>
#include <climits>
using namespace std;
ifstream f("pscnv.in");
ofstream g("pscnv.out");
#define dim 8192
#define nmax 250001
int pz, n, m, x, y, a, b, c, poz[nmax], pond[nmax], mini;
struct muchie{
    int nod, cost;
};
char ax[dim];
vector<muchie> v[nmax];
vector<int> d[1002];
void cit(int &x) {
    x = 0;
    while (ax[pz] < '0' || ax[pz] > '9') {
        if (++pz == dim) f.read(ax, dim), pz = 0;
    }
    while (ax[pz] >= '0' && ax[pz] <= '9') {
        x = x * 10 + ax[pz] - '0';
        if (++pz == dim) f.read(ax, dim), pz = 0;
    }
}
void adaug(int nod) {
    swap(d[mini][0],d[mini][d[mini].size() - 1]);
    poz[d[mini][0]] = 0;
    d[mini].pop_back();
    for (int i = 0; i < v[nod].size(); ++i) {
        x = v[nod][i].nod;
        if (max(v[nod][i].cost,pond[nod]) < pond[x]) {
            if (pond[x] < INT_MAX) {
                swap(d[pond[x]][poz[x]],d[pond[x]][d[pond[x]].size() - 1]);
                poz[d[pond[x]][poz[x]]] = poz[x];
                d[pond[x]].pop_back();
            }
            pond[x] = max(v[nod][i].cost,pond[nod]);
            d[pond[x]].push_back(x);
            poz[x] = d[pond[x]].size() - 1;
        }
        mini = min(mini,pond[x]);
    }
    while (d[mini].empty() && mini < 1000) ++mini;
}
int main()
{
    cit(n), cit(m), cit(x), cit(y);
    for (int i = 1; i <= m; ++i) {
        cit(a), cit(b), cit(c);
        if (a != y && b != x) {
            muchie l;
            l.nod = b, l.cost = c;
            v[a].push_back(l);
        }
    }
    for (int i = 1; i <= n; ++i) pond[i] = INT_MAX;
    pond[x] = 0, mini = 1;
    d[mini].push_back(x);
    while (!d[mini].empty()) adaug(d[mini][0]);
    g << pond[y] << '\n';
    return 0;
}