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#include <iostream>
#include <iomanip>
#include <cmath>

#define PAWN 'O'

using namespace std;

unsigned long long get_sum_of_all_vertices(int n, int m, int k)
{
    unsigned long long sum = 2 * n * m - n - m;
    for (int p = 2; p <= k; ++p)
    {
        sum = sum * (n * m - p) / (p - 1);
    }
    return sum;
}

unsigned long long get_degree(bool **tab, int n, int m)
{
    unsigned long long d = 0;
    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < m; ++j)
        {
            if (tab[i][j])
            {
                if (i > 0 && !tab[i - 1][j]) // move up available
                {
                    ++d;
                }
                if (i < n - 1 && !tab[i + 1][j]) // move down available
                {
                    ++d;
                }
                if (j > 0 && !tab[i][j - 1]) // move left available
                {
                    ++d;
                }
                if (j < m - 1 && !tab[i][j + 1]) // move right available
                {
                    ++d;
                }
            }
        }
    }
    return d;
}

int main()
{
    int n, m;
    cin >> n >> m;

    char c;
    int initialCoordsSum = 0;
    int pawns = 0;
    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < m; ++j)
        {
            cin >> c;
            if (c == PAWN)
            {
                initialCoordsSum += i + j;
                ++pawns;
            }
        }
    }

    bool **tab = new bool *[n];
    int endCoordsSum = 0;
    for (int i = 0; i < n; ++i)
    {
        tab[i] = new bool[m];
        for (int j = 0; j < m; ++j)
        {
            cin >> c;
            tab[i][j] = c == PAWN;
            if (c == PAWN)
            {
                endCoordsSum += i + j;
            }
        }
    }

    if ((initialCoordsSum % 2) != (endCoordsSum % 2))
    {
        cout << 0 << endl;
        for (int i = 0; i < n; ++i)
        {
            delete[] tab[i];
        }
        delete[] tab;
        return 0;
    }

    unsigned long long dsum = get_degree(tab, n, m);
    unsigned long long sum_deg = get_sum_of_all_vertices(n, m, pawns);

    double prob = static_cast<double>(dsum) / static_cast<double>(sum_deg);

    cout << fixed << setprecision(16) << prob << endl;

    for (int i = 0; i < n; ++i)
    {
        delete[] tab[i];
    }
    delete[] tab;
    return 0;
}