#define taskname "D"
#include <bits/stdc++.h>
#define ld long double

using namespace std;
const int maxn = 1510;
const ld pi = acos(-1.0L), arc = 2.5 * pi;
int a[maxn][maxn], n, m;
ld dp[maxn][maxn];

/**
(1, 1)
(2*n+1, 2*m+1)
**/

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);
    cin>>n>>m;
    char c;
    for (int i=1; i<=n; i++) for (int j=1; j<=m; j++) cin>>c, a[i][j] = (c == 'O');
    for (int i=1; i<=2*n+1; i++) for (int j=1; j<=2*m+1; j++) dp[i][j] = 1e18;
    dp[1][1] = 0;
    for (int i=1; i<=2*n+1; i++)
        for (int j=1; j<=2*m+1; j++)
        {
            if (!(i & 1) && !(j & 1)) continue;
            int ci = i/2, cj = j/2;
            if (max(ci, cj) == 0) continue;
            if (i > 1) dp[i][j] = min(dp[i][j], dp[i-1][j] + 5);
            if (j > 1) dp[i][j] = min(dp[i][j], dp[i][j-1] + 5);
            if ((i & 1 || j & 1)&& a[ci][cj]) dp[i][j] = min(dp[i][j], dp[i-1][j-1] + arc);
//            cerr<<i<<" "<<j<<" "<<dp[i][j]<<"\n";
        }
    cout<<fixed<<setprecision(10)<<dp[2*n+1][2*m+1];
}