#pragma ide diagnostic ignored "misc-no-recursion"

#include "bits/stdc++.h"

using namespace std;
typedef long long ll;
typedef double db;

#define TESTCASE 0

static constexpr int MOD = 998'244'353;
static constexpr int INF = 1e9;
static constexpr int MAX_N = 2 * 705;
static constexpr db EPS = 1e-9;

static void solve([[maybe_unused]] int tc) {

    int N, M;
    cin >> N >> M;

    static char grid[MAX_N][MAX_N];
    for (int i = 0; i < N; i++) {
        cin >> grid[i];
    }

    static bool vis[MAX_N][MAX_N];

    priority_queue<tuple<db, int, int>> Q;
    Q.emplace(0, 0, 0);

    while (!Q.empty()) {
        auto [d, x, y] = Q.top();
        Q.pop();

        if (x > 2 * N || y > 2 * M) continue;

        if (vis[x][y]) continue;
        vis[x][y] = true;

        if (x == 2 * N && y == 2 * M) {
            cout << setprecision(15) << (-10 * d) << endl;
            return;
        }

        if (x % 2 == 0) {
            Q.emplace(d - .5, x, y + 1);
        }
        if (y % 2 == 0) {
            Q.emplace(d - .5, x + 1, y);
        }

        if ((x + y) % 2 == 1 && grid[x / 2][y / 2] == 'O') {
            Q.emplace(d - M_PI_4, x + 1, y + 1);
        }
    }
}

int main() {
    ios::sync_with_stdio(false);

    if (const char *f = getenv("REDIRECT_STDOUT"); f) {
        freopen(f, "w", stdout);
    }

    int T = 1;
#if TESTCASE
    cin >> T;
#endif

    for (int t = 1; t <= T; t++) {
        solve(t);
    }

    return 0;
}