#include <bits/stdc++.h>

using namespace std;

const int N = 1400 + 3;
#define check_min(a, b) if(b < a) a = b;
const double PI = acos((double)-1);

double dp[N][N];
string s[N];
int h, w;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> h >> w;
    for(int i = 0; i < h; ++i)
        cin >> s[i];

    for(int i = 2 * h; i >= 0; --i){
        for(int j = 2 * w; j >= 0; --j){
            double &ans = dp[i][j];
            ans = 1e9;

            if(i == 2 * h && j == 2 * w){
                ans = 0;
                continue;
            }

            if(i % 2 == 1 && j % 2 == 1)
                continue;
            if(i % 2 == 0 && j % 2 == 0){
                if(i < 2 * h)
                    check_min(dp[i][j], dp[i + 1][j] + 5);
                if(j < 2 * w)
                    check_min(dp[i][j], dp[i][j + 1] + 5);
            }
            else if(i % 2 == 1){
                check_min(dp[i][j], dp[i + 1][j] + 5);
                if(s[i / 2][j / 2] == 'O' && j < 2 * w)
                check_min(dp[i][j], dp[i + 1][j + 1] + (double)5 / 2 * PI);
            }
            else{
                check_min(dp[i][j], dp[i][j + 1] + 5);
                if(s[i / 2][j / 2] == 'O' && i < 2 * h)
                check_min(dp[i][j], dp[i + 1][j + 1] + (double)5 / 2 * PI);
            }
        }
    }

    cout << fixed << setprecision(9) << dp[0][0] << "\n";
}