#include <iostream>
#include<utility>
#include <vector>
#include <map>
#include<string>
#include<queue>
#include<math.h>
#define pb push_back
#define all(x) begin(x),end(x)
#define gall(x) begin(x),end(x),greater<>()
#define ll long long
#define P pair<int,int>
#define lP pair<ll,ll>
#include <iostream>
#include <vector>
using namespace std;
vector<pair<long long, long long> > prime_factorize(long long N) {
vector<pair<long long, long long> > res;
for (long long p = 2; p * p <= N; ++p) {
        if (N % p != 0) {
            continue;
        }
        int e = 0;
        while (N % p == 0) {
            ++e;
            N /= p;
        }
        res.emplace_back(p, e);
    }
    if (N != 1) {
        res.emplace_back(N, 1);
    }
    return res;
}

using namespace std;
int main() {
    int n,m;
    cin>>n>>m;
    vector<int> x(n+1);
    for(int i=1;i<=n;i++){
        x[i]=i;
    }
    for(int i=0;i<m;i++){
        int a,b;
        cin>>a>>b;
        for(int j=1;j<=n;j++){
            if (b==x[j]) x[j]=0;
        }
    }
    int ans=0;
    for(int j=1;j<=n;j++){
        if(x[j]!=0) ans++;
    }
    cout<<ans<<endl;
    return 0;
}