#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long long unsigned llu;
typedef long double ld;
typedef pair<ll,ll> prl;

#define fi first
#define se second
#define mp make_pair
#define pb push_back

const ll maxN = ll(800);
const ll inf = ll(2e18 + 100);
const ld arc = 2.5*M_PI;

struct Tpoint
{
    ll x, y;
    ld dist;
};

auto compare = [](Tpoint a, Tpoint b)
{
    return a.dist > b.dist;
};

priority_queue <Tpoint, vector<Tpoint>, decltype(compare)> q {compare};

ld len[maxN][maxN] = {0};
bool checked[2*maxN][2*maxN] = {0};

int main()
{
    ll h, w;
    cin >> h >> w;
    char ch;
    for (ll i = 0; i < h; i++) {
        for (ll j = 0; j < w; j++) {
            cin >> ch;
             if (ch == 'X') {
                len[j][i] = 10;
            } else {
                len[j][i] = arc;
            }
        }
    }

    Tpoint tmp;
    tmp.x = 1;
    tmp.y = 0;
    tmp.dist = 5;
    q.push(tmp);

    tmp.x = 0;
    tmp.y = 1;
    tmp.dist = 5;
    q.push(tmp);

    checked[0][0] = true;

    Tpoint newP;
    while ((q.top().x != 2*w || q.top().y != 2*h - 1) && (q.top().x != 2*w - 1 || q.top().y != 2*h)) {
        if (checked[q.top().x][q.top().y]) {
            q.pop();
            continue;
        }

        Tpoint p = q.top();
        checked[q.top().x][q.top().y] = true;
        q.pop();

        if (p.x > 0 && p.y > 0 && !checked[p.x-1][p.y-1]) {
            newP.x = p.x - 1;
            newP.y = p.y - 1;
            if (p.x % 2 == 0) {
                newP.dist = p.dist + len[p.x/2 - 1][p.y/2];
            } else {
                newP.dist = p.dist + len[p.x/2][p.y/2 - 1];
            }
            q.push(newP);
        }

        if (p.x < 2*w && p.y > 0 && !checked[p.x+1][p.y-1]) {
            newP.x = p.x + 1;
            newP.y = p.y - 1;
            if (p.x % 2 == 0) {
                newP.dist = p.dist + len[p.x/2][p.y/2];
            } else {
                newP.dist = p.dist + len[p.x/2][p.y/2 - 1];
            }
            q.push(newP);
        }

        if (p.x < 2*w && p.y < 2*h && !checked[p.x+1][p.y+1]) {
            newP.x = p.x + 1;
            newP.y = p.y + 1;
            if (p.x % 2 == 0) {
                newP.dist = p.dist + len[p.x/2][p.y/2];
            } else {
                newP.dist = p.dist + len[p.x/2][p.y/2];
            }
            q.push(newP);
        }

        if (p.x > 0 && p.y < 2*h && !checked[p.x-1][p.y+1]) {
            newP.x = p.x - 1;
            newP.y = p.y + 1;
            if (p.x % 2 == 0) {
                newP.dist = p.dist + len[p.x/2 - 1][p.y/2];
            } else {
                newP.dist = p.dist + len[p.x/2][p.y/2];
            }
            q.push(newP);
        }

        if (p.x % 2 == 0) {
            if (p.y > 1 && !checked[p.x][p.y-2]) {
                newP.x = p.x;
                newP.y = p.y - 2;
                newP.dist = p.dist + 10;
                q.push(newP);
            }

            if (p.y < 2*h - 1 && !checked[p.x][p.y+2]) {
                newP.x = p.x;
                newP.y = p.y + 2;
                newP.dist = p.dist + 10;
                q.push(newP);
            }
        } else {
            if (p.x > 1 && !checked[p.x-2][p.y]) {
                newP.x = p.x - 2;
                newP.y = p.y;
                newP.dist = p.dist + 10;
                q.push(newP);
            }

            if (p.x < 2*w - 1 && !checked[p.x+2][p.y]) {
                newP.x = p.x + 2;
                newP.y = p.y;
                newP.dist = p.dist + 10;
                q.push(newP);
            }
        }
    }

    cout << setprecision(15);
    cout << q.top().dist + 5 << endl;

    return 0;
}