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

#define MAXN ((int) 2e5)

const int N = 2890;
const int M = 5e4 + 10;
typedef long long ll;
typedef double db;
typedef pair<int, int>pii;
typedef pair<long, long>pll;
int dx[4] = { 0, 1, 0, -1 }, dy[4] = { 1, 0, -1, 0 };
const int mod = 1e9 + 7;
inline long long read()
{
	long long w = 1;
	long long q = 0;
	char ch = ' ';
	while (ch != '-' && (ch < '0' || ch>'9')) ch = getchar();
	if (ch == '-') w = -1, ch = getchar();
	while (ch >= '0' && ch <= '9')
		q = q * 10 + ch - '0', ch = getchar();
	return w * q;
}

const long double pr = 7.853981633975;
int n, m;
int s[N][N];
long double ans = 100000.0;
void dfs(int x, int y, int ban, int quan)
{
	
	if (x > 2 * n+1 || y > 2 * m+1) return;

	if (x == 2 * n+1 and y == 2 * m+1)
	{
		ans = min(ans, ban * 5.0 + quan * pr) ;
	
		return;
	}


	if (s[x][y] == 1)
	{
		dfs(x + 1, y, ban + 1, quan);
		dfs(x, y + 1, ban + 1, quan);
	}
	else if (s[x][y] == 2)
	{
		dfs(x + 1, y + 1, ban, quan + 1);
		dfs(x, y + 1, ban + 1, quan);
	}
	else if (s[x][y] == -2)
	{
		dfs(x + 1, y + 1, ban, quan + 1);
		dfs(x + 1, y, ban + 1, quan);
		
	}
	else if (s[x][y] == -1)
	{
		dfs(x + 1, y, ban + 1, quan);
		dfs(x, y + 1, ban + 1, quan);
	}
	else if (s[x][y] == 0)
	{
		dfs(x + 1, y, ban + 1, quan);
		dfs(x, y + 1, ban + 1, quan);
	}
	

}

	
void sovle()
{
	
	cin >>n >> m;
	
	for (int i = 1; i <= 2*n; i+=2)
	{
		for (int j = 1; j <=2* m; j+=2)
		{
			char ch;

			cin >> ch;
			if (ch == 'X')
			{
				s[i][j] = 1;
				s[i + 1][j] =1;
				s[i][j + 1] = 1;
				s[i + 1][j + 1] = 1;
			}
			else
			{
				s[i][j] = -1;
				s[i + 1][j] = -2;
				s[i][j + 1] = 2;
				s[i + 1][j + 1] = -11;
			}
		}
	}

	dfs(1, 1,0,0);
	
	printf(" % .10lf\n", ans);
	/*for (int i = 1; i <= 2 * n; i++)
	{
		for (int j = 1; j <= 2 * m; j++)
			cout << s[i][j] << "\t";
		cout << endl;
	}*/
}
int main()
{
	int tcase= 1;
	//cin>>tcase;
	while (tcase--)
	{
		sovle();

	}
	return 0;
}