H

#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
using namespace std;

int n, m;
const int maxn = 105;
int mp[maxn][maxn];

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    memset(mp, 0, sizeof(mp));
    cin >> n >> m;
    for(int i = 0;i < m;i++){
        int  x, y;
        cin >> x >> y;
        mp[x][y] = 1;
        mp[y][x] = -1;
    }

    for(int i = 1;i <= n;i++){
        for(int j = 1;j <= n;j++){
            for(int k = 1;k <= n;k++){
                if(mp[j][i] == mp[i][k] && mp[j][i] != 0){
                    mp[j][k] = mp[j][i];
                }
            }
        }
    }
    int ans = 0;
    for(int i = 1;i <= n;i++){
        int sum = 0;
        for(int j = 1;j <= n;j++){
            if(mp[i][j] != 0){
                sum++;
            }
        }
        if(sum == n-1){
            ans++;
        }
    }
    cout << ans << endl;

    return 0;
}

floyed