#include <bits/stdc++.h>

const int INF = 0x3f3f3f3f;

const int MAXN =  + ;

const int MAXE =  + ;

inline void read(int &x)

{

    x = ;char ch = getchar();char c = ch;

    while(ch > '' || ch < '')c = ch, ch = getchar();

    while(ch <= '' && ch >= '')x = x *  + ch - '', ch = getchar();

    if(c == '-')x = -x;

}

inline void swap(int &a, int &b)

{

    int tmp = a;

    a = b;

    b = tmp;

}

struct Edge{int u,v,next;}edge[MAXE << ];

int head[MAXN], cnt, n, m, root;

void insert(int a,int b){edge[++cnt] = Edge{a, b, head[a]};head[a] = cnt;}

int tmp1, tmp2;

int b[MAXN];

int p[MAXN][];

int deep[MAXN];

void dfs(int u, int step)

{

    for(int pos = head[u];pos;pos = edge[pos].next)

    {

        int v = edge[pos].v;

        if(!b[v])

        {

            b[v] = true;

            deep[v] = step + ;

            p[v][] = u;

            dfs(v, step + );

        }

    }

}

void yuchuli()

{

    b[root] = true;

    deep[] = ;

    dfs(root, );

    for(int j =;( << j) <= n;j ++)

        for(int i =;i <= n;i ++)

            p[i][j] = p[p[i][j - ]][j - ];

}

int lca(int va, int vb)

{

    if(deep[va] < deep[vb])swap(va, vb);

    int M = ;

    for(;( << M) <= n;M ++);

    M --;

    for(int i = M;i >= ;i --)

        if(deep[va] - ( << i) >= deep[vb])

            va = p[va][i];

    if(va == vb)return va;

    for(int j = M;j >= ;j --)

    {

        if(p[va][j] != p[vb][j])

        {

            va = p[va][j];

            vb = p[vb][j];

        }

    }

    return p[va][];

}

int main()

{

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

    for(int i = ;i < n;i ++)

    {

        read(tmp1);read(tmp2);

        insert(tmp1, tmp2);

        insert(tmp2, tmp1);

    }

    yuchuli();

    for(int i = ;i <= m;i ++)

    {

        read(tmp1);read(tmp2);

        printf("%d\n", lca(tmp1, tmp2));

    }

    return ;

}