#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
typedef double D;
const D pi = acos(-1.);
const D c = pi / 4;
int n, m;
const int N = 1411;
int code(const double & x, const double & y) {
	return (int)(y * 2 + 0.5) + ((int)(x * 2 + 0.5)) * (2 * m + 1);
}
bool vst[N * N];
D dis[N * N];
const D inf = 1e9;
vector<pair<int, D> > e[N * N];
char a[N][N];
void connect(double x, double y, double X, double Y, double z) {
	int a = code(x, y);
	int b = code(X, Y);
	e[a].pb({b, z});
	e[b].pb({a, z});
}
int main() {
	scanf("%d%d", &n, &m);
	for(int i = 0; i < n; i++) {
		scanf("%s", a[i]);
		for(int j = 0; j < m; j++) {
			if(a[i][j] == 'X') { 
				connect(i, j, i + 0.5, j, 0.5);
				connect(i + 1, j, i + 0.5, j, 0.5);
				connect(i, j, i, j + 0.5, 0.5);
				connect(i, j + 0.5, i, j + 1, 0.5);
			} if(a[i][j] == 'O') {
				connect(i, j, i + 0.5, j, 0.5);
				connect(i + 1, j, i + 0.5, j, 0.5);
				connect(i, j, i, j + 0.5, 0.5);
				connect(i, j + 0.5, i, j + 1, 0.5);

				connect(i + 0.5, j, i, j + 0.5, c);
				connect(i + 0.5, j, i + 1, j + 0.5, c);
				connect(i + 0.5, j + 1, i, j + 0.5, c);
				connect(i + 0.5, j + 1, i + 1, j + 0.5, c);
			}
		}
	}
	for(int i = 0; i < n; i++) {
		int j = m;
		connect(i, j, i + 0.5, j, 0.5);
		connect(i + 1, j, i + 0.5, j, 0.5);
	}
	for(int j = 0; j < m; j++) {
		int i = n;
		connect(i, j, i, j + 0.5, 0.5);
		connect(i, j + 0.5, i, j + 1, 0.5);
	}
	int s = code(0, 0), t = code(n, m);
	priority_queue<pair<D, int> > pq;
	for(int i = 0; i <= t; i++) {
		dis[i] = inf;
	}
	pq.push({0, s});
	dis[s] = 0;
	for(;;) {
		while(!pq.empty() && vst[pq.top().se]) {
			pq.pop();
		}
		if(pq.empty()) break;
		int v = pq.top().se;
		vst[v] = true;
		if(v == t) break;
		pq.pop();
		for(auto & tmp : e[v]) {
			int y = tmp.fi;
			D z = tmp.se;
			if(dis[v] + z < dis[y]) {
				dis[y] = dis[v] + z;
				pq.push({-dis[y], y});
			}
		}
	}
	printf("%.12f\n", (double)dis[t] * 10);
}