#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n, m; cin >> n >> m;
	dsu uf(n);
	vector<int>in(n), out(n);
	rep(i, m) {
		int u, v; cin >> u >> v;
		u--, v--;
		uf.merge(u, v);
		in[u]++;
		out[v]++;
	}
	auto g = uf.groups();
	int ans = -1;
	for (auto v : g) {
		int sub = 0;
		bool chk = false;
		for (auto e : v) {
			if (in[e])chk = true;
			sub += abs(in[e] - out[e]);
		}
		if (!chk)continue;
		sub /= 2;
		ans += max(0, sub - 1) + 1;
	}
	cout << ans << endl;
	return 0;
}