#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define rep2(i, x, n) for (int i = x; i <= n; i++)
#define rep3(i, x, n) for (int i = x; i >= n; i--)
#define each(e, v) for (auto &e : v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
// const int MOD = 998244353;
const int inf = (1 << 30) - 1;
const ll INF = (1LL << 60) - 1;
template <typename T>
bool chmax(T &x, const T &y) {
    return (x < y) ? (x = y, true) : false;
};
template <typename T>
bool chmin(T &x, const T &y) {
    return (x > y) ? (x = y, true) : false;
};

struct io_setup {
    io_setup() {
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

template <typename T>
void print(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << (i == n - 1 ? '\n' : ' ');
}

template <typename T>
void printn(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << '\n';
}

template <typename T>
int lb(const vector<T> &v, T x) {
    return lower_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
int ub(const vector<T> &v, T x) {
    return upper_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
void unique(vector<T> &v) {
    sort(begin(v), end(v));
    v.erase(unique(begin(v), end(v)), end(v));
}

template <typename T>
vector<int> iota(const vector<T> &v, bool greater = false) {
    int n = v.size();
    vector<int> ret(n);
    iota(begin(ret), end(ret), 0);
    sort(begin(ret), end(ret), [&](int i, int j) { return greater ? v[i] > v[j] : v[i] < v[j]; });
    return ret;
}

struct Union_Find_Tree {
    vector<int> data;
    const int n;

    Union_Find_Tree(int n) : data(n, -1), n(n) {}

    int root(int x) {
        if (data[x] < 0) return x;
        return data[x] = root(data[x]);
    }

    int operator[](int i) { return root(i); }

    bool unite(int x, int y) {
        x = root(x), y = root(y);
        if (x == y) return false;
        if (data[x] > data[y]) swap(x, y);
        data[x] += data[y], data[y] = x;
        return true;
    }

    int size(int x) { return -data[root(x)]; }

    bool same(int x, int y) { return root(x) == root(y); }

    void clear() { fill(begin(data), end(data), -1); }
};

int main() {
    int N, M;
    cin >> N >> M;

    vector<int> x(M), y(M);
    vector<vector<int>> idx(N), idy(N);

    rep(i, M) {
        cin >> x[i] >> y[i];
        x[i]--, y[i]--;
        idx[x[i]].eb(y[i]);
        idy[y[i]].eb(x[i]);
    }

    Union_Find_Tree uf(N);
    rep(i, N) {
        int K = sz(idy[i]);
        rep(j, K - 1) { uf.unite(idy[i][j], idy[i][j + 1]); }
    }

    vector<vector<int>> s(N);
    vector<int> cx(N, 0), cy(N, 0);

    rep(i, N) {
        int u = uf[i];
        each(e, idx[i]) s[u].eb(e);
        cy[u]++;
    }

    rep(i, N) {
        unique(s[i]);
        cx[i] = sz(s[i]);
    }
    int K = N - accumulate(all(cx), 0);
    rep(i, K) cx.eb(1), cy.eb(0);

    vector<int> dp(N + 1, -inf);
    dp[0] = 0;
    rep(i, N + 1) {
        rep3(j, N, 0) {
            if (dp[j] == -inf) continue;
            chmax(dp[j + cx[i]], dp[j] + cy[i]);
        }
    }

    int ans = inf;
    rep2(i, 0, N) {
        if (dp[i] != -inf) chmin(ans, N * (i + N - dp[i]) - i * (N - dp[i]));
    }

    cout << ans - M << '\n';
}