#include<bits/stdc++.h>
using namespace std;
vector<int>v[100005];
vector<int>a[100008];
queue<int>q;
int z,color[100008];
void bfs(int source)
{
    int i,level=1,u;
    a[level].push_back(source);
    color[source]=1;
    q.push(source);
    level++;
   while(!q.empty())
   {
         u=q.front();
        q.pop();
    for(i=0;i<v[u].size();i++)
    {
        if(color[v[u][i]]==0)
        {
            q.push(v[u][i]);
            color[v[u][i]]=1;
            a[level].push_back(v[u][i]);
        }
    }
    level++;
   }


}
int main()
{
   int n,i,x,y;
   scanf("%d",&n);
   for(i=1;i<=n-1;i++)
   {
       scanf("%d %d",&x,&y);
       v[x].push_back(y);
       v[y].push_back(x);
   }
   scanf("%d",&z);
   bfs(1);
   printf("%d\n",a[z].size());
   return 0;
}