#include<iostream>
#include <bits/stdc++.h>

# define ld long double
#define ll long long
#define IO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;
const int N = 2 * 700 + 5, mod = 998244353, M = 17;

char a[N][N];
int n, m;
ld dis[N][N];
ld unit = 2.5 * acos(-1);

ld solve() {
    for (int i = 0; i <= 2 * n; i++) {
        for (int j = 0; j <= 2 * m; j++) {
            dis[i][j] = 1e9;
        }
    }
    dis[0][0] = 0;
    priority_queue<pair<ld, pair<int, int> >> q;
    q.push({0, {0, 0}});
    while (!q.empty()) {
        int x = q.top().second.first;
        int y = q.top().second.second;
        if (x == 2 * n && y == 2 * m) {
            return -q.top().first;
        }
        q.pop();
        if (x % 2 == 0 && y + 1 <= 2 * m && dis[x][y + 1] > dis[x][y] + 5) {
            dis[x][y + 1] = dis[x][y] + 5;
            q.push({-dis[x][y + 1], {x, y + 1}});
        }
        if (y % 2 == 0 && x + 1 <= 2 * n && dis[x + 1][y] > dis[x][y] + 5) {
            dis[x + 1][y] = dis[x][y] + 5;
            q.push({-dis[x + 1][y], {x + 1, y}});
        }

        if (a[x / 2][y / 2] == 'O' && x + 1 <= 2 * n && y + 1 <= 2 * m && (x%2 || y%2)) {
            if (dis[x + 1][y + 1] > dis[x][y] + unit) {
                dis[x + 1][y + 1] = dis[x][y] + unit;
                q.push({-dis[x + 1][y + 1], {x + 1, y + 1}});
            }
        }
    }
    return 0;
}

void doWork() {
    cin >> n >> m;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    cout << fixed << setprecision(9) << solve();
}

int main() {
    IO
    int t = 1;
    //  cin >> t;
    for (int i = 1; i <= t; i++) {
        doWork();
    }
}