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#include <bits/stdc++.h>
using namespace std;
#define sim template < class c
#define ris return * this
#define dor > debug & operator <<
#define eni(x) sim > typename \
  enable_if<sizeof dud<c>(0) x 1, debug&>::type operator<<(c i) {
sim > struct rge { c b, e; };
sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c* x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
~debug() { cerr << endl; }
eni(!=) cerr << boolalpha << i; ris; }
eni(==) ris << range(begin(i), end(i)); }
sim, class b dor(pair < b, c > d) {
  ris << "(" << d.first << ", " << d.second << ")";
}
sim dor(rge<c> d) {
  *this << "[";
  for (auto it = d.b; it != d.e; ++it)
	*this << ", " + 2 * (it == d.b) << *it;
  ris << "]";
}
#else
sim dor(const c&) { ris; }
#endif
};
#define imie(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
// debug & operator << (debug & dd, P p) { dd << "(" << p.x << ", " << p.y << ")"; return dd; }

const int M = 65;
unsigned long long C[65][65];

int main() {
	for (int i = 0; i < M; i++) {
		C[i][0] = C[i][i] = 1;
		for (int j = 1; j < i; j++) {
			C[i][j] = C[i-1][j] + C[i-1][j-1];
		}
	}
	int h, w;
	cin >> h >> w;
	vector<string> in(h);
	int count_pawns = 0;
	for (string& row : in) {
		cin >> row;
		for (char c : row) {
			if (c == 'O') {
				count_pawns++;
			}
		}
	}
	vector<string> target(h);
	for (string& row : target) {
		cin >> row;
	}
	
	auto getParity = [&](vector<string> grid) {
		int p = 0;
		for (int row = 0; row < h; row++) {
			for (int col = 0; col < w; col++) {
				if (grid[row][col] == 'O') {
					p += row + col;
				}
			}
		}
		return p % 2;
	};
	
	if (getParity(in) != getParity(target)) {
		puts("0");
		return 0;
	}
	
	#define in ignore_in
	
	int targetDegree = 0;
	for (int row = 0; row < h; row++) {
		for (int col = 0; col < w; col++) {
			if (row + 1 < h && target[row][col] != target[row+1][col]) {
				targetDegree++;
			}
			if (col + 1 < w && target[row][col] != target[row][col+1]) {
				targetDegree++;
			}
		}
	}
	debug() << imie(targetDegree);
	
	// answer = targetDegree / (sum of degrees)
	
	unsigned long long ways = ((h - 1) * w + h * (w - 1)) * C[h*w-2][count_pawns-1];
	printf("%.15lf\n", (double) targetDegree / ways);
	debug() << imie(targetDegree) imie(ways);
	// double p = (double) count_pawns / (h * w) * (h * w - count_pawns) / (h * w - 1);
	// p *= 2;
	// p is probability for a fixed edge to exist
	// debug() << imie(p) imie(ways) imie(p * ways) imie(C[h*w][count_pawns]);
}