#include <vector>
#include <queue>
#include <algorithm>
#include <cstdio>
using namespace std;


const int MaxN = 250001, Inf = 0x3f3f3f3f;

using PII = pair<int, int>;
using VI = vector<int>;
using VB = vector<bool>;
using VP = vector<PII>;
using VVP = vector<VP>;

VVP G;
VI d;
int n,S,F;

void ReadGraph();
void Dijkstra(int S, VI& d);
void Get (int &x);

int main() {

	freopen("pscnv.in","r",stdin);
	freopen("pscnv.out","w",stdout);
    ReadGraph();
    Dijkstra(S, d);
    printf("%d",d[F]);

    return 0;
}

void Dijkstra(int x, VI& d) {
    priority_queue<PII, VP, greater<PII>> Q;
    d = VI(n + 1, Inf);
    d[x] = 0;
    Q.push({0, x});

    int y, w, dx;
    while (!Q.empty())  {
        x = Q.top().second; dx = Q.top().first;
        Q.pop();
        if (d[x] < dx)
            continue;
        for (const PII& p : G[x])  {
            y = p.first;
            w = p.second;
            if (d[y] > max(d[x],w) )   {
                d[y] = max(d[x],w);
                Q.push({d[y], y});
            }
        }

    }
}

void ReadGraph() {
    int m;
    Get(n); Get(m); Get(S); Get(F);
    G = VVP(n + 1);
    int x, y, w;
    while (m--) {
        Get(x); Get(y); Get(w);
        G[x].push_back({y, w});
    }
}
const int Lim = 1000000;
int u =  Lim - 1;
char s[Lim];

void Next () {
    if (++u == Lim)
        std::fread(s, 1, Lim, stdin), u = 0;
}

void Get (int &x) {
    for (; s[u] < '0' || s[u] > '9'; Next());
    for (x = 0; s[u] >= '0' && s[u] <= '9'; Next())
           x = x * 10 + s[u] - '0';
}