#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
	int n, m;
	cin >> n >> m;
	vector<int> in(n), out(n);
	rep(i,m){
		int u, v;
		cin >> u >> v;
		--u;--v;
		in[v]++;
		out[u]++;
	}
	vector<int> diff(n);
	rep(i,n) diff[i] = in[i] - out[i];
	int cnt = 0;
	rep(i,n){
		if(diff[i]>0) cnt += diff[i];
	}
	cout << max(0,cnt-1) << endl;
	return 0;
}