#include <bits/stdc++.h>

using namespace std;

#define all(v) v.begin(), v.end()
typedef long long ll;
using ld = long double;
const int NMAX = 1e5 + 5;


void chmax(int &a, int b){
    a = max(a, b);
}


void chmin(int &a, int b){
    a = min(a, b);
}


string a[3];
const int inf = 1e9;
int self_dist[8] = {inf, inf, inf, 1, inf, 4, 1, 1};
int adj[8][8];
void f(int b1, int b2){
    int res = inf;
    for (int i=0;i<3;i++){
        if (!(b1 & (1 << i))) continue;
        for (int j=0;j<3;j++){
            if (!(b2 & (1 << j))) continue;
            int d = abs(i - j);
            chmin(res, d * d);
        }
    }
    adj[b1][b2] = res;
}


bool valid(int m, int i){
    for (int j=0;j<3;j++){
        if (a[j][i] == '#' && m & (1 << j)) return false;
    }
    return true;
}


int n, k;
int dp[111][333][8][8];


int main() {
    std::ios_base::sync_with_stdio(false); std::cin.tie(nullptr); cout.tie(0);

    cin>>n>>k;
    for (int i=0;i<3;i++){
        cin >> a[i];
        a[i] = "#" + a[i];
    }

    for (int i=0;i<8;i++){
        for (int j=0;j<8;j++){
            f(i, j);
        }
    }

    dp[0][0][0][0] = inf;
    for (int r=1;r<=n;r++){
        for (int j=0;j<=r;j++){
            for (int l=0;l<r;l++){
                for (int b=0;b<8;b++){
                    if (!valid(b, r)) continue;
                    for (int b1=0;b1<8;b1++){
                        if (!b1 && l) continue;
                        for (int b2=0;b2<8;b2++){
                            int d = r - l;
                            int val = dp[l][j][b1][b2];
                            val = min(val, adj[b1][b] + d * d);
                            val = min(val, adj[b2][b] + (d + 1) * (d + 1));
                            val = min(val, self_dist[b]);
                            chmax(dp[r][j + popcount((unsigned int)b)]
                                [b][l + 1 == r ? b1 : 0], val);
                        }
                    }
                }
            }
        }
    }

    int ans = 0;
    for (int i=0;i<8;i++){
        for (int j=0;j<8;j++){
            ans = max(ans, dp[n][k][i][j]);
        }
    }
    cout<<fixed<<setprecision(13);
    if (!ans) cout<<"-1";
    else cout<<sqrt(ans);

    return 0;
}