#include <bits/stdc++.h>

#define endl            '\n'
#define pb             push_back
#define fill(x, y)     memset(x, y, sizeof(x))
#define all(x)         (x).begin(), (x).end()
#define debug(x)       { cerr << #x << " = " << x << endl; }
#define IO	       { ios_base::sync_with_stdio(false); cin.tie(0); }
#define read(x)	       freopen(x, "r", stdin)
#define write(x)       freopen(x, "w", stdout)

using namespace std;

typedef long long      ll;
typedef pair<int, int> ii;
typedef vector<int>    vi;

const double inf = 1e18;
const double pi = acos(-1);

void solve() {
    int h, w;
    cin >> h >> w;

    vector<string> grid(h);
    for (int i=0; i<h; i++) cin >> grid[i];

    vector<vector<double>> dist(2*h + 2, vector<double> (2*w + 2, inf));
    dist[0][0] = 0;
    for (int i=0; i<2*h+1; i++) dist[i][0] = i * 5.0;
    for (int j=0; j<2*w+1; j++) dist[0][j] = j * 5.0;

    for (int i=0; i<h; i++) {
        for (int j=0; j<w; j++) {
            dist[i*2+1][j*2 + 2] = min(dist[i*2 + 1][j*2 + 1], dist[i*2][j*2 + 2]) + 5;
            if (grid[i][j] == 'O') dist[i*2+1][j*2 + 2] = min(dist[i*2+1][j*2 + 2], dist[i*2][j*2 + 1] + (pi * 5.0 / 2.0 ));
            dist[i*2+2][j*2 + 1] = min(dist[i*2+2][j*2], dist[i*2+1][j*2+1]) + 5;
            if (grid[i][j] == 'O') dist[i*2 + 2][j*2 + 1] = min(dist[i*2 + 2][j*2 + 1], dist[i*2+1][j*2] + (pi * 5.0 / 2.0 ));
            dist[2*i+2][2*j+2] = min(dist[2*i + 1][2*j+2], dist[2*i+2][2*j+1]) + 5;
            //cout << dist[2*i+2][2*j+2] << " ";
        }
        //cout << endl;
    }

    cout << dist[2*h][2*w] << endl;

}

int main() {
    IO;
    cout << fixed << setprecision(10);
    solve();
}