//LCA:Doubly

 #include<cstdio>

 #define swap(a,b) a^=b^=a^=b

 #define maxn 500010

 using namespace std;

 int n,m,s,tot,head[maxn],deep[maxn],p[maxn][];

 struct node

 {

     int nxt,to;

 }edge[maxn<<];

 int read()

 {

     int x=,f=;

     char c=getchar();

     while (c<||c>)

         f=c=='-'?-:,c=getchar();

     while (c>=&&c<=)

         x=(x<<)+(x<<)+(c^),c=getchar();

     return x*f;

 }

 void write(int x)

 {

     if (x<)

         x=-x,putchar('-');

     if (x>=)

         write(x/);

     putchar(x%+);

 }

 void add(int a,int b)

 {

     edge[++tot]=(node){head[a],b};

     head[a]=tot;

     edge[++tot]=(node){head[b],a};

     head[b]=tot;

 }

 void init()

 {

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

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

             if (p[i][j-])

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

 }

 int dfs(int u)

 {

     for (int i=head[u];i;i=edge[i].nxt)

         if (!deep[edge[i].to])

         {

             deep[edge[i].to]=deep[u]+;

             p[edge[i].to][]=u;

             dfs(edge[i].to);

         }

 }

 int LCA(int a,int b)

 {

     if (deep[a]<deep[b])

         swap(a,b);

     int i,j;

     for (i=;(<<i)<=deep[a];i++);

     i--;

     for (j=i;j>=;j--)

         if (deep[b]<=deep[a]-(<<j))

             a=p[a][j];

     if (a==b)

         return a;

     for (j=i;j>=;j--)

         if (p[a][j]!=p[b][j]&&deep[p[a][j]]>=)

         {

             a=p[a][j];

             b=p[b][j];

         }

     return p[a][];

 }

 int main()

 {

     int i,j,k;

     n=read(),m=read(),s=read();

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

         add(read(),read());

     deep[s]=;

     dfs(s);

     init();

     while (m--)

         write(LCA(read(),read())),putchar();

     return ;

 }