#include<cstdio>

 #include<algorithm>

 using namespace std;

 const int maxn=,inf=1e9;

 int n,m,x,y,root,tot,dep[maxn],son[maxn],size[maxn],fa[maxn],top[maxn],last[maxn];

 struct edge{int to,pre;}e[maxn<<];

 inline void read(int &k){

     k=; int f=; char c=getchar();

     while(c<''||c>'')c=='-'&&(f=-),c=getchar();

     while(''<=c&&c<='')k=k*+c-'',c=getchar();

     k*=f;

 }

 void add(int x,int y){e[++tot].to=y; e[tot].pre=last[x]; last[x]=tot;}

 void dfs1(int x){

     size[x]=; dep[x]=dep[fa[x]]+;

     for (int i=last[x],to;i;i=e[i].pre)

     if ((to=e[i].to)!=fa[x]){

         fa[to]=x; dfs1(to);

         size[x]+=size[to];

         if (size[to]>size[son[x]]) son[x]=to;

     }

 }

 void dfs2(int x,int tp){

     top[x]=tp;

     if (son[x]) dfs2(son[x],tp);

     for (int i=last[x],to;i;i=e[i].pre)

     if ((to=e[i].to)!=fa[x]&&to!=son[x]) dfs2(to,to);

 }

 int lca(int x,int y){

     int f1=top[x],f2=top[y];

     while(f1!=f2){

         if (dep[f1]<dep[f2]) swap(x,y),swap(f1,f2);

         x=fa[f1]; f1=top[x];

     }

     return dep[x]<dep[y]?x:y;

 }

 int main(){

     read(n); read(m); read(root);

     for (int i=;i<n;i++) read(x),read(y),add(x,y),add(y,x);

     dfs1(root); dfs2(root,root);

     for (int i=;i<=m;i++) read(x),read(y),printf("%d\n",lca(x,y));

     return ;

 }