#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define subnb true
#define Lnb true
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
const ld PI = 3.1415926535897;
const int N = (int)1405, INF = (int)1e9;

int n, m;
string str[N];
ld dp[N][N];

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

    cin >> n >> m;
    rep(i, 0, n) {
        cin >> str[i];
    }
    dp[0][0] = 0;
    rep(i, 0, 2 * n + 1) {
        rep(j, 0, 2 * m + 1) {
            if(i == 0 && j == 0) continue;
            dp[i][j] = INF;
            if(i % 2 == 0 && j % 2 == 0) {
                if(i) dp[i][j] = min(dp[i][j], dp[i - 1][j] + 5);
                if(j) dp[i][j] = min(dp[i][j], dp[i][j - 1] + 5);
            } else if(i % 2 == 1 && j % 2 == 0) {
                if(i) dp[i][j] = min(dp[i][j], dp[i - 1][j] + 5);
                if(i && j) dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + (str[(i - 1) / 2][(j - 1) / 2] == 'X' ? 10 : 2.5 * PI));
            } else if(i % 2 == 0 && j % 2 == 1) {
                if(j) dp[i][j] = min(dp[i][j], dp[i][j - 1] + 5);
                if(i && j) dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + (str[(i - 1) / 2][(j - 1) / 2] == 'X' ? 10 : 2.5 * PI));
            }
        }
    }
    cout << fixed << setprecision(10) << dp[2 * n][2 * m] << '\n';
}