#include <bits/stdc++.h>
#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
#include <iomanip>
#include<set>
#include <numeric>
#include<string>
using ll = long long;
using namespace std;

int main()
{
    ll n, m, cnt;
    cin >> n >> m;
    vector<ll> g(n+1);
    for (int i = 0; i < m; i++){
        int out, in;
        cin >> out >> in;
        g[in]++;
    }
    for (int i = 1; i < n + 1; i++){
        if(g[i] == 0) cnt++;
    }
    cout << cnt << endl;
}