#include <bits/stdc++.h>

#define endl '\n'
#define DEBUG_VAR(x) { cerr << "* "#x" = " << x << endl; }
#define DEBUG_FMT(...) { cerr << "* "; fprintf(stderr, __VA_ARGS__); }

using namespace std;
using LL = long long;
using PII = pair<int, int>;
using PDII = pair<double, pair<int, int>>;

const int N = 2048;
constexpr double PI = acos(-1);

int n, m;

double dis[N][N];
bool vis[N][N];

char a[N][N];

void Dijstra()
{
	for(int i = 1; i <= 2*n+1; i++) 
		for(int j = 1; j <= 2*m+1; j++) {
			dis[i][j] = 1e9;
			vis[i][j] = false;
		}

	priority_queue<PDII, vector<PDII>, greater<PDII>> q;
	q.push({5, {2, 1}}); q.push({5, {1, 2}});
	dis[2][1] = dis[1][2] = 5;

	while(q.size()) {
		auto [x, y] = q.top().second; q.pop();
		if(vis[x][y]) continue;

		vis[x][y] = true;
		// DEBUG_FMT("dis(%d, %d) = %lf\n", x, y, dis[x][y]);

		int nx = x+1, ny = y+1;

		if(nx >= 1 && nx <= 2*n+1 && ny >= 1 && ny <= 2*m+1) {
			char c = a[nx/2][ny/2]; 
			double z;
			if(c == 'X') z = 10;
			else z = 2.5*PI;

			if(dis[nx][ny] > dis[x][y]+z) {
				dis[nx][ny] = dis[x][y]+z;
				q.push({dis[nx][ny], {nx, ny}});
			}
		} 

		nx = x-1, ny = y+1;
		if(nx >= 1 && nx <= 2*n+1 && ny >= 1 && ny <= 2*m+1) {
			char c = a[nx/2][ny/2]; 
			double z;
			if(c == 'X') z = 10;
			else z = 2.5*PI;

			if(dis[nx][ny] > dis[x][y]+z) {
				dis[nx][ny] = dis[x][y]+z;
				q.push({dis[nx][ny], {nx, ny}});
			}
		} 

		if(y&1) nx = x+2, ny = y;
		else nx = x, ny = y+2;
		if(nx >= 1 && nx <= 2*n+1 && ny >= 1 && ny <= 2*m+1) {
			double z = 10;
			if(dis[nx][ny] > dis[x][y]+z) {
				dis[nx][ny] = dis[x][y]+z;
				q.push({dis[nx][ny], {nx, ny}});
			}
		} 
	}
}

int main()
{
	// freopen("1.in", "r", stdin);

	cin >> n >> m;
	for(int i = 1; i <= n; i++) {
		scanf(" %s", a[i]+1);
	}
	Dijstra();

	printf("%.13lf", min(dis[2*n+1][2*m], dis[2*n][2*m+1])+5);
	return 0;
}