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#include <bits/stdc++.h>

using namespace std;


void read_board(int n, int m, vector<string> &board) {
  for (int i = 0; i < n; i++) {
    string s;
    cin >> s;
    board.push_back(s);
  }
}

int npawns(vector<string> &board) {
  int r = 0;
  for (int i = 0; i < board.size(); i++) {
    for (int j = 0; j < board[i].size(); j++) {
      if (board[i][j] == 'O') {
        r++;
      }
    }
  }
  return r;
}

int parity(vector<string> &board) {
  int r = 0;
  for (int i = 0; i < board.size(); i++) {
    for (int j = 0; j < board[i].size(); j++) {
      if (board[i][j] == 'O') {
        r += i + j;
      }
    }
  }
  return r % 2;
}

int degree(vector<string> &board) {
  int r = 0;
  int n = board.size();
  int m = board[0].size();
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (i < n - 1 && board[i][j] != board[i + 1][j]) {
        r++;
      }
      if (j < m - 1 && board[i][j] != board[i][j + 1]) {
        r++;
      }
    }
  }
  return r;
}

long long int binom(long long int n, long long int k) {
  long long int ret = 1;
  for (long long int m = n; m > n - k; m--) {
    ret *= m;
  }
  for (long long int l = 1; l <= k; l++) {
    ret /= l;
  }
  return ret;
}


int main() {
  int n, m;
  scanf("%d%d", &n, &m);

  vector<string> start;
  vector<string> end;

  read_board(n, m, start);
  read_board(n, m, end);

  if (parity(start) != parity(end)) {
    puts("0");
    return 0;
  }

  int k = npawns(end);
  int deg = degree(end);
  long long int nedges = binom(n * m - 2, k - 1) * (2 * n * m - n - m);
  long double out = (long double)deg / (long double)nedges;
  printf("%.15lf\n", (double)out);
}