#include<bits/stdc++.h>
using namespace std;
const int maxn = 2e6 + 5;
const double r = 5, pi = acos(-1), eps = 1e-9;
int Dcmp(double x) {
    return x < -eps ? -1 : x > eps ? 1 : 0;
}
int h, w, id, s, t, idx[705][705][4];
double dis[maxn];
vector<pair<int, double> > G[maxn];
char mp[705][705];
void Add(int u, int v, double w) {
// cerr << u << " -> " << v << " " << w << endl;
    G[u].push_back({v, w});
    G[v].push_back({u, w});
}
struct Node {
    double d;
    int u;
    Node(double d = 0, int u = 0) : d(d), u(u) {}
    bool operator < (const Node &rhs) const {
        return Dcmp(d - rhs.d) > 0;
    }
};
priority_queue<Node>q;
int main() {
    scanf("%d%d", &h, &w);
    for(int i = 1; i <= h; ++ i) {
        scanf("%s", mp[i] + 1);
    }
    for(int i = 1; i <= h; ++ i) {
        for(int j = 1; j <= w; ++ j) {
            for(int k = 0; k < 4; ++ k) {
                idx[i][j][k] = ++ id;
            }
        }
    }
    s = ++ id;
    t = ++ id;
    fill(dis + 1, dis + t + 1, 1e18);
    Add(s, idx[1][1][0], r);
    Add(s, idx[1][1][1], r);
    Add(idx[h][w][2], t, r);
    Add(idx[h][w][3], t, r);
    for(int i = 1; i <= h; ++ i) {
        for(int j = 1; j <= w; ++ j) {
            double d = mp[i][j] == 'X' ? r * 2 : r * pi / 2;
// cerr << i << " " << j << " " << d << endl;
            for(int k = 0; k < 4; ++ k) {
                int nk = (k + 1) % 4;
                Add(idx[i][j][k], idx[i][j][nk], d);
            }
            if(i < h) {
                Add(idx[i][j][3], idx[i + 1][j][1], 0);
                Add(idx[i][j][0], idx[i + 1][j][0], r * 2);
                Add(idx[i][j][2], idx[i + 1][j][2], r * 2);
            }
            if(j < w) {
                Add(idx[i][j][2], idx[i][j + 1][0], 0);
                Add(idx[i][j][1], idx[i][j + 1][1], r * 2);
                Add(idx[i][j][3], idx[i][j + 1][3], r * 2);
            }
        }
    }
    q.push(Node(dis[s] = 0, s));
    while(!q.empty()) {
        Node nd = q.top();
        q.pop();
        if(Dcmp(dis[nd.u] - nd.d) != 0)
            continue;
        for(auto [v, w] : G[nd.u]) {
            if(Dcmp(dis[v] - (nd.d + w)) > 0) {
                q.push(Node(dis[v] = nd.d + w, v));
            }
        }
    }
    printf("%.15f\n", dis[t]);
}