#pragma GCC optimize("Ofast")
#pragma GCC optimize("O3")

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

#define el '\n'
#define F first
#define S second

typedef long long ll;
typedef long double ld;

bool multipleTestCases = 0, sublime = 0;
const int N = 2e3 + 5, INF = 1e9 + 5, mod = 1e9 + 7, LOG = 22, SQ = 500;

int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};

int n, m;
char a[N][N];
ld dist[N][N];

const ld pi = acos(-1) / 2;

bool valid(int i, int j) {
    return i >= 0 and i <= n and j >= 0 and j <= m;
}

ld dijk() {
    for (int i = 0; i <= n; i++) {
        for (int j = 0; j <= m; j++) {
            dist[i][j] = 2e9;
        }
    }

    priority_queue<pair<ld, pair<int, int>>> q;
    q.push({0, {0, 0}});
    dist[0][0] = 0;

    while (q.size()) {
        ld d = -q.top().F;
        int i = q.top().S.F, j = q.top().S.S;
        q.pop();

        if (fabs(d - dist[i][j]) > 1e-6) {
            continue;
        }

        if (i % 2 == 0 and j % 2 == 0) {
            for (int k = 0; k < 4; k++) {
                int ni = i + dx[k], nj = j + dy[k];

                if (valid(ni, nj) and dist[ni][nj] > dist[i][j] + 5) {
                    dist[ni][nj] = dist[i][j] + 5;
                    q.push({-dist[ni][nj], {ni, nj}});
                }
            }
        }
        else if (i % 2 == 0 and j % 2 == 1) {
            if (valid(i, j + 1) and dist[i][j + 1] > dist[i][j] + 5) {
                dist[i][j + 1] = dist[i][j] + 5;
                q.push({-dist[i][j + 1], {i, j + 1}});
            }
            if (valid(i, j - 1) and dist[i][j - 1] > dist[i][j] + 5) {
                dist[i][j - 1] = dist[i][j] + 5;
                q.push({-dist[i][j - 1], {i, j - 1}});
            }

            if (i > 0 and a[i / 2 - 1][j / 2] == 'O') {
                // i - 1, j - 1
                if (valid(i - 1, j - 1) and dist[i - 1][j - 1] > dist[i][j] + 5 * pi) {
                    dist[i - 1][j - 1] = dist[i][j] + 5 * pi;
                    q.push({-dist[i - 1][j - 1], {i - 1, j - 1}});
                }
                // i - 1, j + 1
                if (valid(i - 1, j + 1) and dist[i - 1][j + 1] > dist[i][j] + 5 * pi) {
                    dist[i - 1][j + 1] = dist[i][j] + 5 * pi;
                    q.push({-dist[i - 1][j + 1], {i - 1, j + 1}});
                }
            }
            if (i < n and a[i / 2][j / 2] == 'O') {
                // i + 1, j - 1
                if (valid(i + 1, j - 1) and dist[i + 1][j - 1] > dist[i][j] + 5 * pi) {
                    dist[i + 1][j - 1] = dist[i][j] + 5 * pi;
                    q.push({-dist[i + 1][j - 1], {i + 1, j - 1}});
                }
                // i + 1, j + 1
                if (valid(i + 1, j + 1) and dist[i + 1][j + 1] > dist[i][j] + 5 * pi) {
                    dist[i + 1][j + 1] = dist[i][j] + 5 * pi;
                    q.push({-dist[i + 1][j + 1], {i + 1, j + 1}});
                }
            }
        }
        else if (i % 2 == 1 and j % 2 == 0) {
            if (valid(i + 1, j) and dist[i + 1][j] > dist[i][j] + 5) {
                dist[i + 1][j] = dist[i][j] + 5;
                q.push({-dist[i + 1][j], {i + 1, j}});
            }

            if (j > 0 and a[i / 2][j / 2 - 1] == 'O') {
                // i - 1, j - 1
                if (valid(i - 1, j - 1) and dist[i - 1][j - 1] > dist[i][j] + 5 * pi) {
                    dist[i - 1][j - 1] = dist[i][j] + 5 * pi;
                    q.push({-dist[i - 1][j - 1], {i - 1, j - 1}});
                }
                // i + 1, j - 1
                if (valid(i + 1, j - 1) and dist[i + 1][j - 1] > dist[i][j] + 5 * pi) {
                    dist[i + 1][j - 1] = dist[i][j] + 5 * pi;
                    q.push({-dist[i + 1][j - 1], {i + 1, j - 1}});
                }
            }
            if (j < m and a[i / 2][j / 2] == 'O') {
                // i - 1, j + 1
                if (valid(i - 1, j + 1) and dist[i - 1][j + 1] > dist[i][j] + 5 * pi) {
                    dist[i - 1][j + 1] = dist[i][j] + 5 * pi;
                    q.push({-dist[i - 1][j + 1], {i - 1, j + 1}});
                }
                // i + 1, j + 1
                if (valid(i + 1, j + 1) and dist[i + 1][j + 1] > dist[i][j] + 5 * pi) {
                    dist[i + 1][j + 1] = dist[i][j] + 5 * pi;
                    q.push({-dist[i + 1][j + 1], {i + 1, j + 1}});
                }
            }
        }
    }

    return dist[n][m];
}

void doWork() {
    cin >> n >> m;

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            cin >> a[i][j];
        }
    }

    n = 2 * n;
    m = 2 * m;

    cout << fixed << setprecision(12) << dijk() << el;
}

signed main() {
#ifdef ONLINE_JUDGE
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#endif
#ifndef ONLINE_JUDGE
    if (sublime) {
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    }
#endif
    int tests = 1;
    if (multipleTestCases) {
        cin >> tests;
    }
    for (int tc = 1; tc <= tests; tc++) {
        doWork();
    }
}