#pragma GCC optimize("Ofast","unroll-loops","omit-frame-pointer","inline")
#pragma GCC option("arch=native","tune=native","no-zero-upper")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2")
#pragma GCC optimize(3)
#include<bits/stdc++.h>
#define N 400010
#define rep(i,l,r) for(int i=l;i<=r;i++)
#define drep(i,r,l) for(int i=r;i>=l;i--)
using namespace std;
int rd() {
	int res=0,f=1;char ch=getchar();
	while(ch<'0'||ch>'9') {if(ch=='-') f*=-1;ch=getchar();}
	while(ch>='0'&&ch<='9') res=(res<<1)+(res<<3)+(ch^48),ch=getchar();
	return res*f;
}
const int M=2e3+5;
const double Pi =acos(-1);
int n,m;
char s[M][M];
double dp[M][M];
int main() {
	n=rd(),m=rd();
	for(int i=1; i<=n; ++i)scanf("%s",s[i]+1);
	for(int i=0; i<=n*2+1; ++i)
		for(int j=0; j<=m*2+1; ++j)
			dp[i][j]=1e9;
	for(int i=1; i<=n+1; ++i) {
		for(int j=1; j<=m+1; ++j) {
			dp[i*2-1][j*2-1]=min(dp[i*2-1][j*2-2]+5,dp[i*2-2][j*2-1]+5);
			if(i==1&&j==1)dp[i*2-1][j*2-1]=0;
			if(i<=n) {
				if(s[i][j-1]=='O')dp[i*2][j*2-1]=min(dp[i*2-1][j*2-1]+5,dp[i*2-1][j*2-2]+2.5*Pi);
				else dp[i*2][j*2-1]=dp[i*2-1][j*2-1]+5;
			}
			if(j<=m) {
				if(s[i-1][j]=='O')dp[i*2-1][j*2]=min(dp[i*2-1][j*2-1]+5,dp[i*2-2][j*2-1]+2.5*Pi);
				else dp[i*2-1][j*2]=dp[i*2-1][j*2-1]+5;
			}
		}
	}printf("%.8f",dp[n*2+1][m*2+1]);
	return 0;
}