#include <bits/stdc++.h>

using namespace std;
using LL = long long;
using ULL = unsigned long long;
using VI = vector<int>;
using VL = vector<LL>;
using PII = pair<int, int>;
using PLL = pair<LL, LL>;
using ld = long double;

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define MP make_pair
#define PB push_back
#define EB emplace_back
#define F first
#define S second
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define FILL(a, b) memset(a, b, sizeof(a))

const double pi = acos(-1);

void solve()
{
	int h, w;
	cin >> h >> w;
	vector<string> v(h + 1, "");
	FOR (i, 0, h) 
	{
		cin >> v[i];
		v[i] += 'X';
	}
	FOR (i, 0, w + 1) v[h] += 'X';
	
	vector<vector<double>> d(2 * h + 2, vector<double>(2 * w + 2, 7474 + 7474));
	d[0][0] = 0;
	FOR (i, 0, 2 * h + 1)
	{
		FOR (j, 0, 2 * w + 1)
		{
			int x = i / 2;
			int y = j / 2;
			
			if ((i & 1) && (j & 1)) continue;
			if (i & 1)
			{
				d[i + 1][j] = min(d[i + 1][j], d[i][j] + 5);
				d[i + 1][j + 1] = min(d[i + 1][j + 1], d[i][j] + (v[x][y] == 'O' ? pi * 10 / 4 : 10));
			}
			else if (j & 1)
			{
				d[i][j + 1] = min(d[i][j + 1], d[i][j] + 5);
				d[i + 1][j + 1] = min(d[i + 1][j + 1], d[i][j] + (v[x][y] == 'O' ? pi * 10 / 4 : 10));
			}
			else
			{
				d[i][j + 1] = min(d[i][j + 1], d[i][j] + 5);
				d[i + 1][j] = min(d[i + 1][j], d[i][j] + 5);
			}
		}
	}
	cout << fixed << setprecision(10) << d[2 * h][2 * w] << '\n';
}

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	int t = 1;
	//cin >> t;
	while (t--)
	{
		solve();
	}
}