#include <bits/stdc++.h>
using namespace std;

#define mk make_pair
#define fi first
#define se second

const double PI = acos(-1.0);

int n, m;
string s[705];

vector<pair<int, double> > G[710 * 710 * 2];

int idu(int i, int j) {
	return ((i - 1) * m + j) * 2 - 1;
}
int idd(int i, int j) {
	if (i == n) {
		return n * m * 2 + j;
	} else {
		return (i * m + j) * 2 - 1;
	}
}
int idl(int i, int j) {
	return ((i - 1) * m + j) * 2;
}
int idr(int i, int j) {
	if (j == m) {
		return n * m * 2 + m + i;
	} else {
		return ((i - 1) * m + j + 1) * 2;
	}
}

double dist[710 * 710 * 2];
void dij(int st) {
	for (int i = 1; i <= n * m * 2 + n + m; ++i) {
		dist[i] = 1e9;
	}
	
	dist[st] = 0;
	
	priority_queue<pair<double, int> > que;
	que.push(mk(0, st));
	
	while (!que.empty()) {
		pair<double, int> t = que.top();
		que.pop();
		
		int u = t.se;
		
		if (dist[u] < -t.fi) {
			continue;
		}
		
		for (int i = 0; i < (int)G[u].size(); ++i) {
			int v = G[u][i].fi;
			double w = G[u][i].se;
			
			if (dist[v] > dist[u] + w) {
				dist[v] = dist[u] + w;
				que.push(mk(-dist[v], v));
			}
		}
	}
}

int main() {
	cin >> n >> m;
	for (int i = 1; i <= n; ++i) {
		cin >> s[i];
	}
	
//	for (int i = 1; i <= n; ++i) {
//		for (int j = 1; j <= m; ++j) {
//			cout << idu(i, j) << " ";
//		}
//		cout << endl;
//	}
	
	for (int i = 1; i <= n; ++i) {
		for (int j = 1; j <= m; ++j) {
			if (s[i][j - 1] == 'X') {
				G[idu(i, j)].push_back(mk(idr(i, j), 10));
				G[idu(i, j)].push_back(mk(idl(i, j), 10));
				
				G[idl(i, j)].push_back(mk(idu(i, j), 10));
				G[idl(i, j)].push_back(mk(idd(i, j), 10));
				
				G[idd(i, j)].push_back(mk(idl(i, j), 10));
				G[idd(i, j)].push_back(mk(idr(i, j), 10));
				
				G[idr(i, j)].push_back(mk(idu(i, j), 10));
				G[idr(i, j)].push_back(mk(idd(i, j), 10));
			} else {
				G[idu(i, j)].push_back(mk(idr(i, j), PI * 2.5));
				G[idu(i, j)].push_back(mk(idl(i, j), PI * 2.5));
				
				G[idl(i, j)].push_back(mk(idu(i, j), PI * 2.5));
				G[idl(i, j)].push_back(mk(idd(i, j), PI * 2.5));
				
				G[idd(i, j)].push_back(mk(idl(i, j), PI * 2.5));
				G[idd(i, j)].push_back(mk(idr(i, j), PI * 2.5));
				
				G[idr(i, j)].push_back(mk(idu(i, j), PI * 2.5));
				G[idr(i, j)].push_back(mk(idd(i, j), PI * 2.5));
			}
		}
	}
	for (int i = 1; i <= n; ++i) {
		for (int j = 1; j < m; ++j) {
			G[idu(i, j)].push_back(mk(idu(i, j + 1), 10));
		}
	}
	for (int j = 1; j < m; ++j) {
		G[idd(n, j)].push_back(mk(idd(n, j + 1), 10));
	}
	for (int i = 1; i < n; ++i) {
		for (int j = 1; j <= m; ++j) {
			G[idl(i, j)].push_back(mk(idl(i + 1, j), 10));
		}
	}
	for (int i = 1; i < n; ++i) {
		G[idr(i, m)].push_back(mk(idr(i + 1, m), 10));
	}
	
	dij(idu(1, 1));
	double ans = min(10 + dist[idr(n, m)], 10 + dist[idd(n, m)]);
	
	dij(idl(1, 1));
	ans = min(ans, 10 + dist[idr(n, m)]);
	ans = min(ans, 10 + dist[idd(n, m)]);
	
	cout << setiosflags(ios::fixed) << setprecision(10) << ans << endl;
	
	return 0;
}