#include<bits/stdc++.h>
using namespace std;
#define FOR(i,s,t) for(int i=(s),_t=(t); i<=_t; ++i)
typedef double db;
const db pi=acos(-1);
const int N=705;
char a[N][N];
db b[N][N],c[N][N];
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(9);
    int n,m;
    cin >> n >> m;
    FOR(i,1,n) cin >> a[i]+1;
    FOR(i,1,m) b[0][i]=10*i-5;
    FOR(i,1,n) {
        FOR(j,0,m) c[i][j]=1e9;
        if(i==1) c[i][0]=5;
        FOR(j,0,m) {
            if(i>1) c[i][j]=min(c[i][j],c[i-1][j]+10);
            if(j) c[i][j]=min(c[i][j],b[i-1][j]+(a[i][j]=='X'?10:5*pi/2));
        }
        FOR(j,1,m) b[i][j]=1e9;
        FOR(j,1,m) {
            if(j>1) b[i][j]=min(b[i][j],b[i][j-1]+10);
            b[i][j]=min(b[i][j],c[i][j-1]+(a[i][j]=='X'?10:5*pi/2));
        }
    }
    cout << min(b[n][m],c[n][m])+5 << '\n';
    return 0;
}