#include <bits/stdc++.h>
using namespace std;
#define PI acos(-1)
#define int long long
#define pii pair<int,int>
int n,m;
bool good(int x, int y){
	return x>=0 && x<=2*n && y>=0 && y<=2*m && !(x%2==1 && y%2==1);
}
signed main(){
	cin.tie(nullptr)->sync_with_stdio(false);
	cin >> n >> m;
	vector<string>arr(n);
	for(int i = 0; i<n; i++){
		cin >> arr[i];
	}
	vector<vector<vector<pair<double,pii>>>>adj(n*3,vector<vector<pair<double,pii>>>(m*3));
	vector<vector<double>>dis(n*3,vector<double>(m*3,1e18));
	vector<vector<bool>>vis(n*3,vector<bool>(m*3));
	vector<int>dx = {-1,0,1,0};
	vector<int>dy = {0,1,0,-1};
	for(int i = 0; i<=2*n; i++){
		for(int j = 0; j<=2*m; j++){
			if(!good(i,j))continue;
			for(int d = 0; d<4; d++){
				int x = i+dx[d];
				int y = j+dy[d];
				if(!good(x,y))continue;
				adj[x][y].push_back({0.5,{i,j}});
				adj[i][j].push_back({0.5,{x,y}});
			}
		}
	}
	double rad = PI/4;
	
	for(int i = 0; i<n; i++){
		for(int j = 0; j<m; j++){
			if(arr[i][j]=='X')continue;
			pair<int,int>a = {2*i,2*j+1};
			pair<int,int>b = {2*i+1,2*j};
			pair<int,int>c = {2*i+2,2*j+1};
			pair<int,int>d = {2*i+1,2*j+2};
			adj[a.first][a.second].push_back({rad,b});
			adj[a.first][a.second].push_back({rad,d});
			adj[b.first][b.second].push_back({rad,a});
			adj[b.first][b.second].push_back({rad,c});
			adj[c.first][c.second].push_back({rad,b});
			adj[c.first][c.second].push_back({rad,d});
			adj[d.first][d.second].push_back({rad,c});
			adj[d.first][d.second].push_back({rad,a});
		}
	}
	
	dis[0][0] = 0;
	priority_queue<pair<double,pii>,vector<pair<double,pii>>,greater<pair<double,pii>>>pq;
	pq.push({0,{0,0}});
	while(pq.size()){
		double d = pq.top().first;
		int i = pq.top().second.first;
		int j = pq.top().second.second;
		pq.pop();
		if(vis[i][j])continue;
		vis[i][j] = true;
		for(auto nxt: adj[i][j]){
			double dist = nxt.first + d;

			int x = nxt.second.first;
			int y = nxt.second.second;
			if(dist < dis[x][y]){
				dis[x][y] = dist;
				//cout << nxt.first << ' ' << d << ' ' << x << ' ' << y << '\n';
				pq.push({dis[x][y],{x,y}});
			}
		}
	}
	cout << fixed << setprecision(10);
	cout << dis[2*n][2*m]*10 << '\n';
	return 0;
}