#include<bits/stdc++.h>
using namespace std;
const int N = 1e5 + 3;
vector<tuple<int,int,int>> edges;
int n, m;
set<int> g[N];
void init(int N, int M, vector<int> u, vector<int> v, vector<int> w) {
for (int i = 0; i < M; i++) {
edges.emplace_back(w[i], u[i], v[i]);
}
n = N;
m = M;
}
int getMinimumFuelCapacity(int x, int y) {
auto test = [&](int val) {
for (int i = 0; i < n; i++) g[i].clear();
for (int i = 0; i < m; i++) {
if (get<0>(edges[i]) <= val) {
g[get<1>(edges[i])].insert(get<2>(edges[i]));
g[get<2>(edges[i])].insert(get<1>(edges[i]));
}
}
vector<int> can(2 * n);
can[x] = 1;
deque<int> q = {x};
while (!q.empty()) {
int v = q.front(); q.pop_front();
if (v % n == y) continue;
int type = v / n;
for (auto&u : g[v % n]) {
if (!type && can[u] && !can[u + n]) {
can[u + n] = 1;
q.push_back(u + n);
g[u].erase(v);
}
if (!can[u + type * n]) {
can[u + type * n] = 1;
q.push_back(u + type * n);
g[u].erase(v);
}
}
}
return can[n + y];
};
int l = 0, r = (int)1e9;
while (l <= r) {
int mid = l + r >> 1;
if (test(mid)) r = mid - 1;
else l = mid + 1;
}
if (l == (int) 1e9 + 1) l = -1;
return l;
}
/*
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int N = 5, M = 6;
vector<int> U = {0, 0, 1, 1, 1, 2};
vector<int> V = {1, 2, 2, 3, 4, 3};
vector<int> W = {4, 4, 1, 2, 10, 3};
init(N, M, U, V, W);
int q = 3;
while (q--) {
int x, y;
cin >> x >> y;
cout << getMinimumFuelCapacity(x, y) << "\n" << flush;
}
}*/
