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

#define ll long long
#define all(x) x.begin(), x.end()
#define pb push_back
#define mp make_pair
#define ps push
#define in insert
#define f first
#define s second
#define nl cout<<"\n"
#define ca(v) for(auto i:v) cout<<i<<" ";
#define cbit(x) __builtin_popcount(x)
#define gcd(a, b) __gcd(a, b)
#define lcm(a, b) (a*b/gcd(a, b))
int xm[4] = {-1, 1, 0, 0};
int ym[4] = {0, 0, -1, 1};
const int MOD = 1e9 + 7;
const int MAXN = 5e5 + 5;
const ll POW = 9973;


#define ld long double
#define PI 3.14159265358979323846
// const ld PI = 3.14159265358979323846;

const int MX = 15e2+5;

ld ans[MX][MX];
bool circ[MX][MX];

ld go(int i, int j) {
    if (i<0 || j <0) {
        return MOD;
    }
    return ans[2*i][2*j];
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
    int h,w;cin>>h>>w;
    for(int i=0;i<h;i++) {
        string S;cin>>S;
        for(int j=0;j<w;j++) {
            if(S[j]=='O') {
                circ[i][j] = true;
            }
        }
    }
    
    for (int i=0;i<=2*h;i++) {
        for (int j=0;j<=2*w;j++) {
            ans[i][j]=MOD;
        }
    }
    ans[0][0]=0;
    for (int i=0;i<=2*h;i++) {
        for (int j=0;j<=2*w;j++) {
            if (i%2==0 && j%2==0) {
                ans[i+1][j] = min(ans[i+1][j],ans[i][j] + 0.5);
                ans[i][j+1] = min(ans[i][j+1],ans[i][j] + 0.5);
            }
            if (i%2==1 && j%2==0) {
                ans[i+1][j] = min(ans[i+1][j], ans[i][j]+ 0.5) ;
                if (circ[i/2][j/2]) { //right
                    ans[i+1][j+1] = min(ans[i+1][j+1], ans[i][j]+ PI/4) ;
                }
            }
            if (i%2==0 && j%2==1) {
                ans[i][j+1] = min(ans[i][j+1], ans[i][j]+ 0.5) ;
                if (circ[i/2][j/2]) { //below
                    ans[i+1][j+1] = min(ans[i+1][j+1], ans[i][j]+ PI/4) ;
                }
            }
        }
    }
    cout << setprecision(8) << ans[2*h][2*w]*10 << endl;
    // for (int i=0;i<=h;i++) {
    //     for (int j=0;j<=w;j++) {
    //         if (i && j && circ[i-1][j-1]) {
    //             ans[2*i][2*j] = min(go(i,j-1),go(i-1,j)) +1;
    //             ans[2*i][2*j] = min(ans[2*i][2*j], go(2*i-1,2*j)) +0.5;
    //             ans[2*i][2*j] = min(ans[2*i][2*j], go(2*i,2*j-1)) +0.5;
    //             ans[2*i][2*j-1] = ans[PI/4;
    //         } else {
    //             ans[2*i][2*j] = min(go(i,j-1),go(i-1,j)) +1;
    //             ans[2*i][2*j] = min(ans[2*i][2*j], go(2*i-1,2*j)) +0.5;
    //             ans[2*i][2*j] = min(ans[2*i][2*j], go(2*i,2*j-1)) +0.5;
    //         }
    //     }
    // }
}