#include <bits/stdc++.h>
using namespace std;
const int INF = 1E9 + 7;
template <class C>
void mini(C& a4, C b4) {
  a4 = min(a4, b4);
}
template <class C>
void maxi(C& a4, C b4) {
  a4 = max(a4, b4);
}
const int MN = 1100;
int a[MN], b[MN];
int x[MN];
int y[MN];
int main() {
  ios_base::sync_with_stdio(false);
  long long n, m;
  cin >> n >> m;
  int d = 0;
  long long extra = 0;
  for (int i = 0; i < (n); ++i) x[i] = -1;
  for (int i = 0; i < (m); ++i) y[i] = -1;
  for (int i = 0; i < (n); ++i) {
    string s;
    cin >> s;
    for (int j = 0; j < (m); ++j) {
      if (s[j] == 'X') {
        x[i] = j;
        y[j] = i;
        a[d] = i;
        b[d] = j;
        ++d;
        extra += 4 * (i * (n - i - 1) + j * (m - j - 1));
        extra -= m * (i * (i + 1) / 2 + (n - i) * (n - i - 1) / 2);
        extra -= n * (j * (j + 1) / 2 + (m - j) * (m - j - 1) / 2);
      } else {
        extra += m * (i * (i + 1) / 2 + (n - i) * (n - i - 1) / 2);
        extra += n * (j * (j + 1) / 2 + (m - j) * (m - j - 1) / 2);
      }
    }
  }
  for (int i = 0; i < (d); ++i)
    for (int j = 0; j < (d); ++j) {
      extra += abs(a[i] - a[j]) + abs(b[i] - b[j]);
    }
  for (int i = 0; i < (n); ++i) {
    if (x[i] == -1) continue;
    for (int j = (i + 1); j <= (n - 1); ++j) {
      if (x[j] == -1 || x[j] < x[j - 1]) break;
      extra += 4 * (x[i] * (m - 1 - x[j]));
    }
  }
  for (int i = 0; i < (n); ++i) {
    if (x[i] == -1) continue;
    for (int j = (i + 1); j <= (n - 1); ++j) {
      if (x[j] == -1 || x[j] > x[j - 1]) break;
      extra += 4 * (x[j] * (m - 1 - x[i]));
    }
  }
  for (int i = 0; i < (m); ++i) {
    if (y[i] == -1) continue;
    for (int j = (i + 1); j <= (m - 1); ++j) {
      if (y[j] == -1 || y[j] > y[j - 1]) break;
      extra += 4 * (y[j] * (n - 1 - y[i]));
    }
  }
  for (int i = 0; i < (m); ++i) {
    if (y[i] == -1) continue;
    for (int j = (i + 1); j <= (m - 1); ++j) {
      if (y[j] == -1 || y[j] < y[j - 1]) break;
      extra += 4 * (y[i] * (n - 1 - y[j]));
    }
  }
  long long cnt = ((long long)n * m - d) * (n * m - d);
  long double res = (long double)extra / cnt;
  cout << setprecision(12) << fixed << res << endl;
  return 0;
}
