#include<bits/stdc++.h>
#define int long long
#define endl '\n'
using namespace std;
typedef pair<double,int> PII;
const int N=2000200;
vector<PII> q[2000200];
int n,m,x;
double u=7.8539815;
char s[770][770];
double d[N];
bool st[N];
void bfs(){
	for(int i=1;i<=N;i++){
		d[i]=1000010;
	}
	d[0]=0;
	priority_queue<PII,vector<PII>,greater<PII>> heap;
	heap.push({d[0],0});
	while(heap.size()){
		PII t=heap.top();
		//cout<<t.first<<endl;
		heap.pop();
		int ver=t.second;
		double dis=t.first;
		if(st[ver]) continue;
		st[ver]=1;
		for(auto i:q[ver]){
			int j=i.second;
			double w=i.first;
			//cout<<" "<<j<<" "<<d[j]<<endl;
			if(d[j]>dis+w){
				d[j]=dis+w;
				//cout<<d[j]<<endl;
				heap.push({d[j],j});
			}
		}
	}
}
void solve(){
	cin>>n>>m;
	for(int i=0;i<n;i++){
		for(int j=0;j<m;j++){
			cin>>s[i][j];
		}
	}
	int cnt=0;
	n++;
	m++;
	for(int i=0;i<n;i++){
		for(int j=0;j<m;j++){
			if(j==m-1){
				q[i*4*m+2*j].push_back({5,4*i*m+2*m+j*2});
				q[i*4*m+2*m+2*j].push_back({5,4*i*m+4*m+j*2});
				continue;
			}
			if(i==n-1){
				q[i*4*m+2*j].push_back({5,4*i*m+j*2+1});
				q[i*4*m+2*j+1].push_back({5,4*i*m+j*2+2});
				continue;
			}
			//cout<<" "<<i<<" "<<j<<" "<<i*4*m+2*j<<endl;
			q[i*4*m+2*j].push_back({5,4*i*m+j*2+1});
			q[i*4*m+2*j].push_back({5,4*i*m+2*m+j*2});
			q[i*4*m+2*j+1].push_back({5,4*i*m+j*2+2});
			q[i*4*m+2*m+2*j].push_back({5,4*i*m+4*m+j*2});
			if(s[i][j]=='O'){
				q[i*4*m+2*j+1].push_back({u,4*i*m+2*m+j*2+2});
				q[i*4*m+2*m+2*j].push_back({u,4*i*m+4*m+j*2+1});
			}
		}
	}
	//dfs(int u);
	/*for(auto i:q[80]){
		cout<<i.first<<" "<<i.second<<endl;
	}*/ 
	//cout<<q[12][0].second<<endl;
	bfs();
	//cout<<2*n*(2*m-1)-2<<endl;
	cout<<fixed<<setprecision(7)<<d[(2*n-1)*(2*m)-2]<<endl;
	cout<<endl;
}
signed main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	int T=1;
	//cin>>T;
	while(T--){
		solve();
	}
	return 0;
}
/*
3 5
XOOXO
OXOXO
XXXXO
*/