#include <bits/stdc++.h>

using namespace std;
#define IOS ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr)
#define rep(a, b, c) for(int (a)=(b);(a)<=(c);(a)++)
#define per(a, b, c) for(int (a)=(b);(a)>=(c);(a)--)
#define mset(var, val) memset(var,val,sizeof(var))
#define ll long long
#define fi first
#define se second
#define no "No\n"
#define yes "Yes\n"
#define pb push_back
#define endl "\n"
#define pii pair<int,int>
#define pll pair<ll,ll>
#define dbg(x...) do{cout<<#x<<" -> ";err(x);}while (0)

void err() { cout << '\n'; }

template<class T, class... Ts>
void err(T arg, Ts... args) {
    cout << arg << ' ';
    err(args...);
}


const double inf = 5000.0;
const double one = 2.5*acos(-1.0);
int n, m;
double a[1500][1500];
string s[705];

void solve() {
    cin >> n >> m;
    for(int i = 0; i < n; i++) {
        cin >> s[i];
    }
    for(int i = 0; i < n*2+2; i++) {
        for(int j = 0; j < m*2+2; j++) {
            a[i][j] = inf;
        }
    }
    a[0][0] = 0;
    for(int i = 0; i <= 2*n; i++) {
        for(int j = 0; j <= 2*m; j++) {
            if(((i&1) && (j&1)) || (a[i][j] == inf)) continue;
            if((i&1) || (j&1)) {
                if(s[i/2][j/2] == 'O') {
                    a[i+1][j+1] = min(a[i+1][j+1], a[i][j] + one);
                }
                else if(i&1){
                    a[i+1][j] = min(a[i+1][j], a[i][j] + 5);
                }
                else {
                    a[i][j+1] = min(a[i][j+1], a[i][j] + 5);
                }
            }
            else {
                a[i+1][j] = min(a[i+1][j], a[i][j] + 5);
                a[i][j+1] = min(a[i][j+1], a[i][j] + 5);
            }
        }
    }
    printf("%.10lf\n", a[2*n][2*m]);
}

int main() {
    IOS;
    int T = 1;
    // cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}