#include <bits/stdc++.h>
using namespace std;

struct Edge {
    int u, v;
    long long w;
    bool operator<(const Edge& other) const {
        return w < other.w;
    }
};

struct DSU {
    vector<int> parent;
    DSU(int n) {
        parent.resize(n + 1);
        for (int i = 1; i <= n; i++) parent[i] = i;
    }
    int find(int v) {
        if (v == parent[v]) return v;
        return parent[v] = find(parent[v]);
    }
    bool unite(int a, int b) {
        a = find(a); b = find(b);
        if (a == b) return false;
        parent[b] = a;
        return true;
    }
};

vector<vector<pair<int, long long>>> adj;
long long ans = -1;
int target;

bool dfs(int u, int p, long long max_w) {
    if (u == target) {
        ans = max_w;
        return true;
    }
    for (auto& edge : adj[u]) {
        int v = edge.first;
        long long w = edge.second;
        if (v != p) {
            if (dfs(v, u, max(max_w, w))) return true;
        }
    }
    return false;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n, m;
    if (!(cin >> n >> m)) return 0;
    int s, t;
    cin >> s >> t;
    vector<Edge> edges(m);
    for (int i = 0; i < m; i++) {
        cin >> edges[i].u >> edges[i].v >> edges[i].w;
    }
    sort(edges.begin(), edges.end());
    DSU dsu(n);
    adj.resize(n + 1);
    int edges_used = 0;
    for (auto& e : edges) {
        if (dsu.unite(e.u, e.v)) {
            adj[e.u].push_back({e.v, e.w});
            adj[e.v].push_back({e.u, e.w});
            edges_used++;
            if (edges_used == n - 1) break;
        }
    }

    // Check connectivity in original graph first or via DSU
    if (dsu.find(s) != dsu.find(t)) {
        cout << -1 << "\n";
        return 0;
    }

    target = t;
    dfs(s, 0, 0);
    cout << ans << "\n";
    return 0;
}