#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define fi first
#define se second
#define all(a) a.begin(),a.end()
int main(){
  int n,m;
  cin >> n >> m;
  vector<int> g(n);
  for(int i=0; i<m; ++i){
    int a,b;
    cin >> a >> b;
    g[b-1]++;
  }
  
  int ans=0;
  for(int i=0; i<n; ++i){
    if(g[i]==0) ans++;
  }
  cout << ans << endl;
  return 0;
}