#include<iostream>
#include<vector>
#include<cstring>
using namespace std;
int dp[1001][2];  // assuming maximum number of nodes is 1000, can change it
vector< vector<int> >edges(1001);
/* Initialize dp[][] to be -1 for all values (u,select) */
/* Select is 0 or 1 for false/true respectively        */
 
int func(int node , int select )
{
   if(dp[node][select] != -1)return dp[node][select];
   int ans = 0,i;
 
   // value of node is node number itself
   if(select)ans=node;
 
   //edges[i] stores neighbors of node i
   for(i=0;i<(int)edges[node].size();i++)
   {
      if(select)ans=ans+func(edges[node][i],1-select);
      else ans=ans+max(func(edges[node][i],0),func(edges[node][i],1));
   }
   dp[node][select] = ans;
   return ans;
}
 
// from main call, root is root of tree and answer is
// your final answer
int main()
{
    memset(dp,-1,sizeof(dp));
    int noofedges,root,i,parent,child;
 
    //input takes number of edges and root of the tree in your test case 1
    cin>> noofedges >> root; 
    for(i = 0;i < noofedges ;i++)
    {
        //then each edge is given as parent child
        cin>> parent >> child;
        edges[parent].push_back(child);
    }
    int answer = max(func(root,0),func(root,1));
    cout<< answer <<endl;
 
    // I have taken this kind of input format to make it easy you can change it, not much change will be there
}