#include <iostream>
#include <cstdio>
#include <algorithm>
#include <queue>
#include <map>
#include <cmath>
#include <cstring>
#include <vector>
#include <bitset>

template <typename Tp>
inline void read(Tp &x) {
    x = 0;
    bool f = true; char ch = getchar();
    for ( ; ch < '0' || ch > '9'; ch = getchar()) f ^= ch == '-';
    for ( ; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + (ch ^ 48);
    x = f ? x : -x;
}

const int N = 2e3;
const double pi = acos(-1);

char s[N + 5][N + 5];
int dp[N + 5][N + 5];

int main() {
    int n, m;
    read(n), read(m);
    for (int i = 1; i <= n; ++i) scanf("%s", s[i] + 1);
    for (int i = 1; i <= 2 * n; ++i)
        for (int j = 1; j <= 2 * m; ++j) {
            if ((i & 1) && (j & 1)) continue;
            if (i % 2 == 0 && j % 2 == 0) dp[i][j] = std::max(dp[i - 1][j], dp[i][j - 1]);
            else if (i % 2 == 0) {
                dp[i][j] = dp[i][j - 1];
                if (s[i >> 1][(j + 1) >> 1] == 'O') dp[i][j] = std::max(dp[i][j], dp[i - 1][j - 1] + 1);
            }
            else {
                dp[i][j] = dp[i - 1][j];
                if (s[(i + 1) >> 1][j >> 1] == 'O') dp[i][j] = std::max(dp[i][j], dp[i - 1][j - 1] + 1);
            } 
        }
    double ans = (n + m - dp[2 * n][2 * m]) + pi / 4 * dp[2 * n][2 * m];
    printf("%.10f\n", ans * 10);
    return 0;
}