//详解见https://www.cnblogs.com/zwfymqz/p/7795299.html
//博主： 自为风月马前卒 https://www.cnblogs.com/zwfymqz/
// 洛谷 P3379 最近公共祖先 链接https://www.luogu.org/problem/P3379
1 #include<cstdio>
2 #include<cstring>
3 #include<algorithm>
4 using namespace std;
5
6 const int MAXN = 1e5+10;
7
8 struct node {
9 int v, next;
10 } edge[MAXN];
11
12 int head[MAXN];
13 int num = 1;
14 inline void add_edge(int x, int y) {
15 edge[num].v = y;
16 edge[num].next = head[x];
17 head[x] = num++;
18 }
19
20 int f[MAXN][21];
21 int deep[MAXN];
22 int n, m, root;
23 void dfs(int cur) {
24 for(int i = head[cur]; i != -1; i = edge[i].next) {
25 if(!deep[edge[i].v]) {
26 deep[edge[i].v] = deep[cur] + 1;
27 f[edge[i].v][0] = cur;
28 dfs(edge[i].v);
29 }
30 }
31 }
32
33 void PRE() {
34 for(int j = 1; j <= 19; ++j) {
35 for(int i = 1; i <= n; ++i) {
36 f[i][j] = f[f[i][j-1]][j-1];
37 }
38 }
39 }
40
41 int LCA(int x, int y) {
42 if(deep[x] < deep[y]) swap(x, y);
43 for(int i = 19; i >= 0; --i) {
44 if(deep[f[x][i]] >= deep[y]) {
45 x = f[x][i];
46 }
47 }
48 if(x == y) return x;
49 for(int i = 19; i >= 0; --i) {
50 if(f[x][i] != f[y][i]) {
51 x = f[x][i];
52 y = f[y][i];
53 }
54 }
55 return f[x][0];
56 }
57
58 int main() {
59 memset(head, -1, sizeof(head));
60 scanf("%d%d%d", &n, &m, &root);
61 int x, y;
62 for(int i = 0; i != n-1; ++i) {
63 scanf("%d%d", &x, &y);
64 add_edge(x, y);
65 add_edge(y, x);
66 }
67 deep[root] = 1;
68 dfs(root);
69 PRE();
70 for(int i = 0; i != n; ++i) {
71 scanf("%d%d", &x, &y);
72 printf("%d\n", LCA(x, y));
73 }
74 return 0;
75 }