#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int min_addition(int N, const vector<int>& A) {
	vector<int> poses;
	for (int i = 0; i < 2 * N; i++) {
		if (A[i % N] == 1) {
			poses.push_back(i);
		}
	}
	int L = poses.size() / 2;
	if (L == 0) {
		return (N + 1) / 2;
	}
	int ans = 0;
	for (int i = 0; i < L; i++) {
		int d = poses[i + 1] - poses[i];
		ans += (d - 1) / 2;
	}
	return ans;
}

int solve(int N, int M, const vector<vector<int> >& G) {
	auto dfs = [&](auto& self, int x, int pre) -> pair<int, bool> {
		int sum = 0;
		bool use = false;
		for (int i : G[x]) {
			if (i != pre) {
				pair<int, bool> subres = self(self, i, x);
				sum += subres.first;
				if (!subres.second) {
					use = true;
				}
			}
		}
		sum += int(use);
		return make_pair(sum, use);
	};
	vector<int> A(N);
	int ans = 0;
	for (int i = 0; i < N; i++) {
		pair<int, bool> res = dfs(dfs, i, -1);
		ans += res.first;
		A[i] = int(res.second);
	}
	int subans = min_addition(N, A);
	ans += subans;
	return ans;
}

int main() {
	int N, M;
	cin >> N >> M;
	vector<vector<int> > G(N + M);
	for (int i = 0; i < N + M; i++) {
		int a, b;
		cin >> a >> b;
		if (a >= N || b >= N) {
			G[a].push_back(b);
			G[b].push_back(a);
		}
	}
	int ans = solve(N, M, G);
	cout << ans << endl;
	return 0;
}