// Hey there.. I love you <3
#include <bits/stdc++.h>

using namespace std;
using ll = long long;

mt19937 rnd(time(nullptr));

#define all(x) x.begin(), x.end()

const int N = 1e6 + 5, M = 705, mod = 1e9 + 7;

int l[M][M], r[M][M], up[M][M], dn[M][M];
double dist[N];
vector<pair<int, double>> adj[N];

void add(int u, int v, double w) {
    adj[u].emplace_back(v, w);
    adj[v].emplace_back(u, w);
}

void work() {
    
    int h, w;
    cin >> h >> w;
    int a[h][w];
    for (int i = 0; i < h; ++i)
        for (int j = 0; j < w; ++j) {
            char c;
            cin >> c;
            a[i][j] = c == 'O';
        }
    
    int c = 1;
    
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            l[i][j] = j ? r[i][j - 1] : c++;
            r[i][j] = c++;
        }
    }
    
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            up[i][j] = i ? dn[i - 1][j] : c++;
            dn[i][j] = c++;
        }
    }
    
    
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            double d = a[i][j] ? 7.85398163 : 10;
            add(up[i][j], l[i][j], d);
            add(dn[i][j], l[i][j], d);
            add(up[i][j], r[i][j], d);
            add(dn[i][j], r[i][j], d);
            if (i) {
                if (!j) add(l[i][j], l[i - 1][j], 10);
                add(r[i][j], r[i - 1][j], 10);
            }
            if (j) {
                if (!i) add(up[i][j], up[i][j - 1], 10);
                add(dn[i][j], dn[i][j - 1], 10);
            }
        }
    }
    add(0, up[0][0], 5);
    add(0, l[0][0], 5);
    add(c, dn[h - 1][w - 1], 5);
    add(c, r[h - 1][w - 1], 5);
    
    for (int i = 1; i < N; ++i)
        dist[i] = 1e9;
    
    priority_queue<pair<double, int>, vector<pair<double, int>>, greater<>> pq;
    pq.push({dist[0], 0});
    
    while (!pq.empty()) {
        int u = pq.top().second;
        pq.pop();
        for (auto it: adj[u]) {
            int v = it.first;
            double d = it.second;
            if (dist[u] + d < dist[v])
                pq.push({dist[v] = dist[u] + d, v});
        }
    }
    
    cout << fixed << setprecision(10) << dist[c] << endl;
    
}


void init() {
    cin.tie(nullptr);
    istream::sync_with_stdio(false);
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
    
    
}

int main() {
    init();
    
    int testCases = 1;
    //cin >> testCases;
    while (testCases--) work();
    
    return 0;
}