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#include <bits/stdc++.h>

using namespace std;

int height, width;
int startBlacks = 0;
int endBlacks = 0;
vector<vector<bool>> endPosition;
vector<pair<int, int>> endPawns;

double binomial(int n, int k) {
    double result = 1;
    int i = n;
    while (i > n-k) {
        result *= i;
        i--;
    }
    i = 2;
    while (i <= k) {
        result /= i;
        i++;
    }
    return result;
}

void read() {
    cin >> height >> width;

    char field;
    for (int i = 0; i < height; ++i) {
        for (int j = 0; j < width; ++j) {
            cin >> field;
            if (field == 'O' && (i - j) % 2 == 0) {
                startBlacks++;
            }
        }
    }
    for (int i = 0; i < height; ++i) {
        vector<bool> row;
        for (int j = 0; j < width; ++j) {
            cin >> field;
            row.push_back(field == 'O');
            if (field == 'O') {
                endPawns.emplace_back(i, j);
                if ((i - j) % 2 == 0) {
                    endBlacks++;
                }
            }
        }
        endPosition.push_back(row);
    }
}

int getEndPositionMoves() {
    int result = 0;
    for (auto pawn: endPawns) {
        if (pawn.first > 0 && !endPosition[pawn.first - 1][pawn.second]) {
            result++;
        }
        if (pawn.second > 0 && !endPosition[pawn.first][pawn.second - 1]) {
            result++;
        }
        if (pawn.first + 1 < height && !endPosition[pawn.first + 1][pawn.second]) {
            result++;
        }
        if (pawn.second + 1 < width && !endPosition[pawn.first][pawn.second + 1]) {
            result++;
        }
    }
    return result;
}

double getAllMoves() {
    int singleMoves;
    if (min(height, width) == 1) {
        singleMoves = 2 * max(height, width) - 2;
    } else {
        singleMoves = 8 + 6 * (height + width - 4) + 4 * (height - 2) * (width - 2);
    }
    return singleMoves * binomial(width * height - 2, (int) endPawns.size() - 1);
}

string format(double nominator, double denominator) {
    stringstream ss;
    ss.precision(16);
    ss << fixed;
    ss << nominator / denominator;
    string result = ss.str();
    if (result.find('.') != string::npos) {
        result = result.substr(0, result.find_last_not_of('0') + 1);
        if (result.find('.') == result.size() - 1) {
            result = result.substr(0, result.size() - 1);
        }
    }
    return result;
}

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

    read();
    if (startBlacks % 2 != endBlacks % 2) {
        cout << 0 << endl;
        return 0;
    }
    double nominator = 2.0 * getEndPositionMoves();
    double denominator = getAllMoves();

    cout << format(nominator, denominator) << endl;

    return 0;
}