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

#define fi first
#define se second
#define Mp make_pair

typedef double db;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

const db pi = acos(-1);

signed main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    int n, m;
    cin >> n >> m;
    vector<string> s(n);
    for(int i = 0; i < n; i++)
        cin >> s[i];
    
    vector<vector<pii>> f(2 * n + 10, vector<pii>(2 * m + 10, Mp(1e9, 1e9)));
    f[0][1] = f[1][0] = Mp(1, 0);

    auto get = [&](int i, int j) {
        if(i % 2) {
            return j != 2 * m && s[i / 2][j / 2] == 'O';
        } else {
            return i != 2 * n && s[i / 2][j / 2] == 'O';
        }
    };
    auto val = [&](pii a) -> db {
        return a.fi / 2. + a.se * pi / 4;
    };
    auto pmin = [&](pii a, pii b) -> pii {
        pii t = Mp(a.fi - b.fi, a.se - b.se);
        return val(t) < 0 ? a : b;
    };
    // cerr << "fuck\n";
    for(int sum = 1; sum < 2 * (n + m) - 1; sum += 2) {
        for(int i = min(sum, 2 * n), j = sum - i; i >= 0 && j <= 2 * m; i--, j++) {
            auto [a, b] = f[i][j];
            // cerr << i << ' ' << j << "   " << a << ' ' << b << '\n';
            if(i % 2) { // type 2
                if(i + 2 <= 2 * n) {
                    f[i + 2][j] = pmin(f[i + 2][j], Mp(a + 2, b));
                }
                if(j != 2 * m) {
                    if(get(i, j)) {
                        f[i + 1][j + 1] = pmin(f[i + 1][j + 1], Mp(a, b + 1));
                    } else {
                        f[i + 1][j + 1] = pmin(f[i + 1][j + 1], Mp(a + 2, b));
                    }
                }
            } else {
                if(j + 2 <= 2 * m) {
                    f[i][j + 2] = pmin(f[i][j + 2], Mp(a + 2, b));
                }
                if(i != 2 * n) {
                    if(get(i, j)) {
                        f[i + 1][j + 1] = pmin(f[i + 1][j + 1], Mp(a, b + 1));
                    } else {
                        f[i + 1][j + 1] = pmin(f[i + 1][j + 1], Mp(a + 2, b));
                    }
                }
            }
        }
    }

    pii ans = pmin(f[2 * n - 1][2 * m], f[2 * n][2 * m - 1]);
    ans.fi++;
    // cerr << ans.fi << ' ' << ans.se << '\n';
    cout << setprecision(20) << val(ans) * 10 << '\n';
    return 0;
}
/*
3 5
XOOXO
OXOXO
XXXXO

1 4
XOOX

*/