// This file is a "Hello, world!" in C++ language by GCC for wandbox.
#include<bits/stdc++.h>
using namespace std;
typedef long long int uli;

/*
Dinic is a struct with two methods:
1. AddEdge(u,v,c): adds an edge from u to v with capacity c
2. MaxFlow(s,t): calculates the Maximum Flow with source s and sink t
*/

class Dinic{
private:
    pair<int,pair<int,int>> *Arr;
public:
    Dinic(int n){
        Arr = new pair<int,pair<int,int>>[n];
    }

    void AddEdge(int u, int v, int c){
        pair<int,pair<int,int>> elem;
        elem.first = u;
        elem.second.first =  v;
        elem.second.second = c;
        Arr.pushback(elem);
    }
};

int a[55],b[55];
int main(){
  int n;
  scanf("%d",&n);
  for(int i=0;i<n;i++){
    scanf("%d %d",a+i,b+i);
    --a[i],--b[i];
  }
  int s=n+n;
  int t=s+1;
  int ans=0;
  for(int i=0;i<n;i++){
    //number of people that want to kill i
    int cnt=0;
    for(int j=0;j<n;j++)
      if(a[j]==i || b[j]==i)
        cnt++;
    //if cnt<=1 the werewolf can at least tie
    if(cnt<=1){
      ans++;
      continue;
    }
    Dinic din(n+n+2);
    for(int j=0;j<n;j++)if(j!=i){
      din.AddEdge(s,j,1);
      int cap=cnt-1;
      if(j==a[i] || j==b[i])cap--;
      din.AddEdge(j +n,t,cap);

      if(a[j]!=i && b[j]!=i){
        din.AddEdge(j,a[j] +n,1);
        din.AddEdge(j,b[j] +n,1);
      }
    }
    uli flw=din.MaxFlow(s,t);
    if(flw<n-1-cnt)ans++;
  }
  printf("%d\n",ans);
  return 0;
}