#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vl = vector<ll>;
using sl = set<ll>;
#define ov4(a, b, c, d, name, ...) name
#define rep3(i, a, b, c) for (ll i = (a); i < (b); i += (c))
#define rep2(i, a, b) rep3(i, a, b, 1)
#define rep1(i, n) rep2(i, 0, n)
#define rep0(n) rep1(aaaaa, n)
#define rep(...) ov4(__VA_ARGS__, rep3, rep2, rep1, rep0)(__VA_ARGS__)
#define all(v) v.begin(), v.end()
template <class T>
using vc = vector<T>;
template <class T>
using vvc = vc<vc<T>>;
void solve() {
    ll n, m;
    cin >> n >> m;
    vvc<ll> g(n + m);
    vc<ll> done(n);
    rep(i, n + m) {
        ll u, v;
        cin >> u >> v;
        if (u < n and v < n) continue;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    ll res = 0;
    vc<ll> dp(n + m);
    auto dfs = [&](auto&& dfs, ll from, ll par) -> void {
        for (auto to : g[from]) {
            if (to == par) continue;
            dfs(dfs, to, from);
        }
        if (dp[from] == false and par != -1) dp[par] = 1;
        if (from < n) {
            if (dp[from]) {
                done[from] = true;
            }
        }
    };
    rep(i, n) {
        dfs(dfs, i, -1);
    }
    rep(i, n + m) res += dp[i];
    vc<ll> idx;
    rep(i, n) if (done[i]) idx.push_back(i);
    if (idx.empty()) {
        res += (n + 1) / 2;
    } else {
        idx.push_back(idx[0] + n);
        ll sz = idx.size();
        rep(i, 1, sz) res += (idx[i] - idx[i - 1] -1) / 2;
    }
    cout << res << endl;
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cout << fixed << setprecision(20);
    ll t = 1;
    // cin >> t;
    rep2(_, 0, t) solve();
}