#include <bits/stdc++.h> using namespace std; constexpr int N = 5e5 + 5; int n, m, R, dn, dfn[N], mi[19][N]; vector e[N]; int get(int x, int y) {return dfn[x] < dfn[y] ? x : y;} void dfs(int id, int f) { mi[0][dfn[id] = ++dn] = f; for(int it : e[id]) if(it != f) dfs(it, id); } int lca(int u, int v) { if(u == v) return u; if((u = dfn[u]) > (v = dfn[v])) swap(u, v); int d = __lg(v - u++); return get(mi[d][u], mi[d][v - (1 << d) + 1]); } int main() { scanf("%d %d %d", &n, &m, &R); for(int i = 2, u, v; i <= n; i++) { scanf("%d %d", &u, &v); e[u].push_back(v), e[v].push_back(u); } dfs(R, 0); for(int i = 1; i <= __lg(n); i++) for(int j = 1; j + (1 << i) - 1 <= n; j++) mi[i][j] = get(mi[i - 1][j], mi[i - 1][j + (1 << i - 1)]); for(int i = 1, u, v; i <= m; i++) scanf("%d %d", &u, &v), printf("%d\n", lca(u, v)); return 0; }1. - ~###### ~