#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int h, w;
  cin >> h >> w;
  vector Grid1(h, vector<char>(w)), Grid2(h, vector<char>(w));
  rep(i, h) rep(j, w) cin >> Grid1[i][j];
  rep(i, h) rep(j, w) cin >> Grid2[i][j];
  rep(i, h) rep(j, w) Grid2[i][j] = Grid2[i][j] ^ '.' ^ '#';
  bool rotateOk = true;
  rep(i, h) rep(j, w) if (Grid1[i][j] != Grid2[h - i - 1][w - j - 1]) rotateOk = false;

  // f(x) = x 回目に成功する確率
  function<double(int)> f;
  if (rotateOk) {
    if (Grid1 == Grid2) {
      f = [&](int x) -> double {
        double res = 1;
        rep(i, x - 1) res *= pow(2, -i);
        res *= 1 - pow(2, -(x - 1));
        return res;
      };
    }
    else {
      f = [&](int x) -> double {
        double res = 1;
        // 奇数回目はミス
        rep(i, x - 1) {
          if (i % 2 == 0)
            res *= 1;
          else
            res *= pow(2, -i);
        }
        if (x % 2 == 0)
          res *= 1 - pow(2, -(x - 1));
        else
          res *= 0;
        return res;
      };
    }
  }
  else {
    if (Grid1 == Grid2) {
      f = [&](int x) -> double {
        double res = 1;
        // 偶数回目はミス
        rep(i, x - 1) {
          if (i % 2 == 1)
            res *= 1;
          else
            res *= pow(2, -i);
        }
        if (x % 2 == 1)
          res *= 1 - pow(2, -(x - 1));
        else
          res *= 0;
        return res;
      };
    }
    else {
      // 全ミス
      cout << -1 << endl;
      return 0;
    }
  }
  double ans = 0;
  for (int x = 1; x <= 100; ++x) {
    Debug(x, f(x));
    ans += x * f(x);
  }
  cout << fixed << setprecision(15) << ans << endl;
  return 0;
}