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#include <bits/stdc++.h>

using namespace std;
using LL = long long;
#define FOR(i, l, r) for(int i = (l); i <= (r); ++i)
#define REP(i, n) FOR(i, 0, (n) - 1)
#define ssize(x) int(x.size())

template<class A, class B> auto &operator<<(ostream &o, pair<A, B> p) {
    return o << '(' << p.first << ", " << p.second << ')';
}

template<class T> auto operator<<(ostream &o, T x) -> decltype(x.end(), o) {
    o << '{'; int i = 0; for (auto e : x) o << (", ")+2*!i++ << e;
    return o << '}';
}

#ifdef DEBUG
#define debug(x...) cerr << "[" #x "]: ", [](auto... $) {((cerr << $ << "; "), ...); }(x), cerr << '\n';
#else
#define debug(...) {}
#endif


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m;
    cin >> n >> m;
    vector<vector<char>> vs(n, vector<char>(m)), ve(n, vector<char>(m));
    int coord_s = 0, coord_e = 0, k = 0;
    vector<int> dx = {-1, 0, 1, 0}, dy = {0, -1, 0, 1};

    REP(i, n) {
        REP(j, m) {
            cin >> vs[i][j];
            if (vs[i][j] == 'O') {
                coord_s += i + j;
                k += 1;
            }
        }
    }
    REP(i, n) {
        REP(j, m) {
            cin >> ve[i][j];
            if (ve[i][j] == 'O')
                coord_e += i + j;
        }
    }

    if (coord_s % 2 != coord_e % 2) {
        cout << "0.0\n";
        return 0;
    }

    auto valid = [&](int x, int y) {
        return x >= 0 and y >= 0 and x < n and y < m;
    };

    auto possible_moves = [&](int x, int y) {
        int ans = 0;
        REP(i, 4) {
            auto nx = x + dx[i], ny = y + dy[i];
            ans += valid(nx, ny) and ve[nx][ny] == '.';
        }
        return ans;
    };

    int deg = 0;
    REP(i, n) {
        REP(j, m) {
            if (ve[i][j] == 'O')
                deg += possible_moves(i, j);
        }
    }
    
    auto choose = [&](LL x, LL y) {
        if (x < 0 || y < 0 || x < y)
            return 0LL;
        LL ret = 1;
        for (LL i = 1; i <= y; i++) {
            ret *= x - i + 1;
            ret /= i;
        }
        return ret;;
    };

    auto add_1D = [&](int neighbours) {
        int d = max(n, m);
        if (neighbours == 1)
            return choose(d - 2, k - 1);
        return choose(d - 3, k - 2) * 2 + choose(d - 3, k - 1) * 2;
    };

    auto add = [&](int neighbours) {
        if (n == 1 or m == 1)
            return add_1D(neighbours);
        LL ret = 0;
        FOR(i, 1, neighbours) {
            ret += choose(n * m - neighbours - 1, k - neighbours + i - 1)
                * choose(neighbours, i) * (LL) i;
        }
        return ret;
    };

    LL ev = 0;
    if (n == 1 or m == 1) {
        ev = add(1) * 2 + add(2) * (LL) (max(n, m) - 2);
    } else {
        ev = add(2) * 4
            + add(3) * (LL) (2 * (n + m - 4))
            + add(4) * (LL) ((n - 2) * (m - 2));
    }
    
    cout << fixed << setprecision(15);
    cout << (long double) (2 * deg) / (long double) (ev) << '\n';

    return 0;
}