#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);
	dsu uf(n);
	vector<bool> vis(n);
	rep(i,m){
		int u, v;
		cin >> u >> v;
		--u;--v;
		in[v]++;
		out[u]++;
		uf.merge(u,v);
		vis[u] = true;
		vis[v] = true;
	}
	vector<int> diff(n);
	rep(i,n) diff[i] = in[i] - out[i];
	int cnt = 0;
	vector<vector<int>> ls(n); 
	rep(i,n){
		if(!vis[i]) continue;
		ls[uf.leader(i)].push_back(diff[i]);
	}
	int c = 0;
	rep(i,n){
		int tmp = 0;
		for(int d : ls[i]) {
			if(d>0) tmp += d;
		}
		if(ls[i].size()>=1) c++;
		cnt += tmp;
	}
	cnt += c-1;
	cout << max(0,cnt-1) << endl;
	return 0;
}