#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=3e5+10;
bool flag1[N],flag2[N];
int n,m,a[N],b[N],ans;
signed main(){
	cin>>n>>m;
	for(int i=1;i<=m;i++){
		cin>>a[i]>>b[i];
	}
	for(int i=m;i>=1;i--){
		if(flag1[a[i]]==0 && flag2[b[i]]==0){
			ans++;
		}
		flag1[a[i]]=1;
		flag2[b[i]]=1;
	}
	cout<<ans;
	return 0;
}