#pragma GCC optimize("Ofast") #include <bits/stdc++.h> using namespace std; int n, m, s, root, a, b, dep[500005], fa[500005][20]; vector<int> tr[500005]; void bfs(int root) { memset(dep, 0x3f, sizeof(dep)); dep[0] = 0; dep[root] = 1; queue<int> q; q.push(root); while (!q.empty()) { int t = q.front(); q.pop(); for (int i : tr[t]) { if (dep[i] > dep[t] + 1) { dep[i] = dep[t] + 1; q.push(i); fa[i][0] = t; for (int k = 1; k <= 19; k++) { fa[i][k] = fa[fa[i][k - 1]][k - 1]; } } } } } int lca(int a, int b) { if (dep[a] < dep[b]) swap(a, b); for (int k = 19; k >= 0; k--) { if (dep[fa[a][k]] >= dep[b]) { a = fa[a][k]; } } if (a == b) return a; for (int k = 19; k >= 0; k--) { if (fa[a][k] != fa[b][k]) { a = fa[a][k]; b = fa[b][k]; } } return fa[a][0]; } int main() { scanf("%d%d%d", &n, &m, &root); for (int i = 1; i < n; i++) { scanf("%d%d", &a, &b); tr[a].push_back(b); tr[b].push_back(a); } bfs(root); for (int i = 0; i < m; i++) { scanf("%d%d", &a, &b); printf("%d\n", lca(a, b)); } return 0; }