import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


int root(int[] uf, int u) {
  return (uf[u] < 0) ? u : (uf[u] = uf.root(uf[u]));
}
bool connect(int[] uf, int u, int v) {
  u = uf.root(u);
  v = uf.root(v);
  if (u == v) return false;
  if (uf[u] > uf[v]) swap(u, v);
  uf[u] += uf[v];
  uf[v] = u;
  return true;
}


enum INF = 10^^9;

void main() {
  try {
    for (; ; ) {
      const N = readInt();
      const M = readInt();
      auto X = new int[M];
      auto Y = new int[M];
      foreach (i; 0 .. M) {
        X[i] = readInt() - 1;
        Y[i] = readInt() - 1;
      }
      
      auto uf = new int[N + N];
      uf[] = -1;
      foreach (i; 0 .. M) {
        uf.connect(X[i], N + Y[i]);
      }
      auto as = new int[N + N];
      auto bs = new int[N + N];
      foreach (x; 0 .. N) {
        ++as[uf.root(x)];
      }
      foreach (y; 0 .. N) {
        ++bs[uf.root(N + y)];
      }
      
      auto mn = new int[N + 1];
      auto mx = new int[N + 1];
      mn[] = +INF;
      mx[] = -INF;
      mn[0] = mx[0] = N;
      
      foreach (r; 0 .. N + N) {
        if (uf[r] < 0) {
          foreach_reverse (a; 0 .. N - as[r] + 1) {
            if (mn[a] <= mx[a]) {
              chmin(mn[a + as[r]], mn[a] - bs[r]);
              chmax(mx[a + as[r]], mx[a] - bs[r]);
            }
          }
        }
      }
      
      int ans = INF;
      foreach (a; 0 .. N + 1) {
        if (mn[a] <= mx[a]) {
          foreach (b; [mn[a], mx[a]]) {
            chmin(ans, a * (N - b) + (N - a) * b);
          }
        }
      }
      ans -= M;
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}