#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001



int main(){
	
	int n,m;
	cin>>n>>m;
	vector<int> c(n);
	rep(i,m){
		int a,b;
		cin>>a>>b;
		c[b-1]++;
	}
	int ans = 0;
	rep(i,n){
		if(c[i]==0)ans++;
	}
	cout<<ans<<endl;
	
	return 0;
}