#include <bits/stdc++.h>
using namespace std;

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define MP make_pair
#define PB push_back
#define F first
#define S second

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;

const int N = 474;
const int inf = 4747474;
string v[3];
double dp[N][N][8][8];

double res[8] = {inf, inf, inf, 1, inf, 2, 1, 1};

void setmax(double& a, double b)
{
	a = max(a, b);
}
void setmin(double& a, double b)
{
	a = min(a, b);
}

double f(int mask1, int mask2, int dis)
{
	double ans = inf;
	FOR (i, 0, 3)
	{
		if (((mask1 >> i) & 1) == 0)
			continue;
		FOR (j, 0, 3)
		{
			if (((mask2 >> j) & 1) == 0)
				continue;
				
			int d1 = abs(i - j);
			setmin(ans, sqrt(d1 * d1 + dis * dis));
		}
	}
	
	return ans;
}

bool ok(int m, int i)
{
	FOR (j, 0, 3)
	{
		if (((m >> j) & 1) && v[j][i] == '#')
			return false;
	}
	return true;
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	int n, k;
	cin >> n >> k;
	FOR (i, 0, 3)
	{
		string s;
		cin >> s;
		v[i] = "#" + s;
	}
	FOR (i, 0, n + 1)
	{
		FOR(cnt, 0, k + 1)
		{
			FOR (m1, 0, 8)
			{
				FOR (m2, 0, 8)
					dp[i][cnt][m1][m2] = 0;
			}
		}
	}
	dp[0][0][0][0] = inf;
	FOR (now, 1, n + 1)
	{
		FOR (cnt, 0, k + 1)
		{
			FOR (col, 0, now)
			{
				FOR (m, 0, 8)
				{
					if (!ok(m, now))
						continue;
					FOR (mask, 0, 8)
					{
						if(mask == 0 && col != 0)
							continue;
						FOR (pmask, 0, 8)
						{
							double cur = dp[col][cnt][mask][pmask];
							cur = min(cur, f(mask, m, now - col));
							assert((mask == 0 || m == 0) || f(mask, m, now - col) < inf);
							cur = min(cur, f(pmask, m, now - col + 1));
							assert((pmask == 0 || m == 0) || f(pmask, m, now - col + 1) < inf);
							cur = min(cur, res[m]);
							
							setmax(dp[now][cnt + __builtin_popcount(m)][m][col + 1 == now ? mask : 0], cur);
						}
					}
				}
			}
		}
	}
	
	double ans = 0;
	FOR (i, 0, 8)
	{
		FOR (j, 0, 8)
		{
			ans = max(ans, dp[n][k][i][j]);
		}
	}
	if (ans < 0.1) {
		cout << "-1\n";
	}
	else {
		cout << fixed << setprecision(10) << ans << '\n';
	}
	
	return 0;
}