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

#define ll long long

int main()
{
	cin.tie(0)->sync_with_stdio(false);
	cin.exceptions(ios::badbit | ios::failbit);
	cout << fixed << setprecision(15);
	int h, w;
	cin >> h >> w;
	vector<string> a(h);
	for(auto i = 0; i < h; ++ i){
		cin >> a[i];
	}
	const double inf = 1e18;
	vector dist(2 * h + 1, vector<double>(2 * w + 1, inf));
	dist[0][0] = 0;
	priority_queue<tuple<double, int, int>, vector<tuple<double, int, int>>, greater<>> pq;
	pq.push({0, 0, 0});
	vector done(2 * h + 1, vector<int>(2 * w + 1));
	const double r = 5, arc = acos(-1) * r / 2;
	while(!pq.empty()){
		auto [d, x, y] = pq.top();
		pq.pop();
		if(done[x][y]) continue;
		done[x][y] = true;
		if(x % 2 == 0 && y % 2 == 0){
			if(x + 1 <= 2 * h && dist[x][y] + r < dist[x + 1][y]){
				pq.push({dist[x + 1][y] = dist[x][y] + r, x + 1, y});
			}
			if(y + 1 <= 2 * w && dist[x][y] + r < dist[x][y + 1]){
				pq.push({dist[x][y + 1] = dist[x][y] + r, x, y + 1});
			}
		}
		else if(x % 2 == 0){
			if(y + 1 <= 2 * w && dist[x][y] + r < dist[x][y + 1]){
				pq.push({dist[x][y + 1] = dist[x][y] + r, x, y + 1});
			}
			if(x + 1 <= 2 * h && a[x >> 1][y >> 1] == 'O' && dist[x][y] + arc < dist[x + 1][y + 1]){
				pq.push({dist[x + 1][y + 1] = dist[x][y] + arc, x + 1, y + 1});
			}
		}
		else{
			assert(y % 2 == 0);
			if(x + 1 <= 2 * h && dist[x][y] + r < dist[x + 1][y]){
				pq.push({dist[x + 1][y] = dist[x][y] + r, x + 1, y});
			}
			if(y + 1 <= 2 * w && a[x >> 1][y >> 1] == 'O' && dist[x][y] + arc < dist[x + 1][y + 1]){
				pq.push({dist[x + 1][y + 1] = dist[x][y] + arc, x + 1, y + 1});
			}
		}
	}
	assert(done[2 * h][2 * w]);
	cout << dist[2 * h][2 * w] << "\n";
	return 0;
}