#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=200005;
const double hu=3.14159265358*10/4.0;
int h,w;
string s[705];
double ans[1410][1410];
void solve(){
	cin>>h>>w;
	for(int i=1;i<=h;i++){
		cin>>s[i];
		s[i]=' '+s[i];
	}
	for(int i=0;i<=h*2+5;i++){
		for(int j=0;j<=w*2+5;j++){
			ans[i][j]=1e9;
		}
	}
	ans[0][0]=0;
	for(int i=0;i<=h;i++){
		for(int j=0;j<=w;j++){
			for(int k1=0;k1<=1;k1++){
				for(int k2=0;k2<=1;k2++){
					int x=i*2+k1,y=j*2+k2;
					if(x%2==1&&y%2==1)continue;
					if(x>=1)
						ans[x][y]=min(ans[x][y],ans[x-1][y]+5);
					if(y>=1)
						ans[x][y]=min(ans[x][y],ans[x][y-1]+5);
					
					if(x%2==1&&y%2==0&&x>=1&&y>=1){
						if((s[i+1][j]=='O')){
							ans[x][y]=min(ans[x][y],ans[x-1][y-1]+hu);
						}
					}
					if(x%2==0&&y%2==1&&x>=1&&y>=1){
						if(s[i][j+1]=='O'){
							ans[x][y]=min(ans[x][y],ans[x-1][y-1]+hu);
						}
					}
					
				//	cout<<"i "<<i<<" j "<<j<<" "<<"x: "<<x<<" y "<<y<<" "<<ans[x][y]<<endl;						
				}
			}
		}
	}
	printf("%.10lf",ans[2*h][2*w]);
	return;
}
signed main() {
//	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	//freopen("in.txt","r",stdin);
	//freopen("out.txt","w",stdout);
	int T_case=1;
//	cin>>T_case;
	while(T_case--){
		solve();
	}
    return 0;
}