typedef long long ll;
typedef long double ld;

#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main(){
    ll n,m;
    std::cin >> n>>m;
    vector<ll> nyu(n),shu(n);
    for (int i = 0; i < m; i++) {
        ll u,v;
        std::cin >> u>>v;
        u--;v--;
        shu[u]++;
        nyu[v]++;
    }
    ll p = 0;
    for (int i = 0; i < n; i++) {
        // std::cout << shu[i]<<" "<<nyu[i] << std::endl;
        if(shu[i]-nyu[i]>0){
            p += shu[i]-nyu[i];
        }
    }
    std::cout << max(0ll,p-1) << std::endl;
};