#include<bits/stdc++.h>
//#define int long long
#define endl "\n"
#define ll long long
#define PII std::pair<int,int>
#define pi acos(-1)
using namespace std;
const int maxn = 705;
const int mod = 998244353;
int dp[maxn][maxn];
int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    cout << fixed << setprecision(10);
    int N, M;
    cin >> N >> M;
    vector<vector<char>> G(N + 2, vector<char>(M + 2));
    for (int i = 1; i <= N; ++i) {
        for (int j = 1; j <= M; ++j) {
            cin >> G[i][j];
        }
    }
    for (int i = 1; i <= N + 1; ++i) {
        for (int j = 1; j <= M + 1; ++j) {
            if(i - 1 > 0) dp[i][j] = max(dp[i][j], dp[i - 1][j]);
            if(j - 1 > 0) dp[i][j] = max(dp[i][j], dp[i][j - 1]);
            if (i - 1 > 0 && j - 1 > 0) {
                if (i - 1 >= 1 && j - 1 >= 1 && G[i - 1][j - 1] == 'O' && G[i - 1][j] == 'O')
                    dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 2);
                else if (i - 1 >= 1 && j - 1 >= 1 && G[i - 1][j - 1] == 'O' && G[i][j - 1] == 'O')
                    dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 2);
                else if(i - 1 >= 1 && j - 1 >= 1 && G[i - 1][j - 1] == 'O')
                    dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 1);
            }
        }
    }
    double cnt = 10 - 2 * pi * 5 / 4;
    //cout << cnt << endl;
    //cout << dp[N + 1][M + 1] << endl;
    cout << (N + M) * 1.0 * 10 - dp[N + 1][M + 1] * cnt << endl;
    return 0;
}