#include "bits/stdc++.h"
using namespace std;
#define ff first
#define ss second
#define int long long
#define pii pair<int,int>
#define pb emplace_back
#define rep(i,a,b) for(int i=a; i < b; ++i)
#define owo ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define V vector

#define cerr if(1) cout
#define dbg(x) cerr << "?" << #x << " : " << x << endl;

void solve();
signed main(){
	owo
	int t = 1; //cin >> t
	while(t--) solve();
}

const int N = 105;
const int INF = 1e9;

int n, k;
string g[3];

void chmax(int &x,int y){
	if(x < y) x = y;
}
int sqr(int x){
	return x*x;
}
#define popcount __builtin_popcountll

int smolchk(int lim){
	V<int> dp(1<<6, -INF);
	dp[0] = 0;

	rep(i,0,n){
		V<int> nxt(1<<6, 0);

		int allowed = 0;
		rep(j,0,3) if(g[j][i]=='.'){
			allowed |= 1<<j;
		}

		rep(msk,0,1<<9){
			bool ok = 1;
			ok &= ((msk&0b111)|allowed)==allowed;

			rep(a,0,9) if(msk&1<<a)
			rep(b,0,a) if(msk&1<<b){
				ok &= sqr(a/3-b/3)+sqr(a%3-b%3)>=lim;
			}

			if(ok){
				chmax(nxt[msk&0b111111], dp[msk>>3]+popcount(msk&0b111));
			}
		}

		dp.swap(nxt);
	}

	int ret = 0;
	rep(msk,0,1<<6){
		chmax(ret, dp[msk]);
	}
	return ret;
}


int chk(int lim){
	// dbg(lim);
	if(lim < 9) return smolchk(lim);

	V<int> pos(3,-INF), amt(3,0);

	rep(i,0,n){
		V<int> npos=pos, namt=amt;
		// dbg(i);
		
		rep(now,0,3) if(g[now][i]=='.')
		rep(prv,0,3){
			bool ok = 1;
			ok &= sqr(i-pos[prv]) + sqr(now-prv) >= lim;
			
			// better than previous choices
			ok &= amt[prv]+1 > namt[now];


			if(ok){
				npos[now] = i;
				namt[now] = amt[prv]+1;
			}
		}

		pos.swap(npos);
		amt.swap(namt);
		// dbg(i);
	}

	int ret = 0;
	rep(i,0,3){
		chmax(ret, amt[i]);
	}
	// dbg(ret);
	return ret;
}

void solve(){
	cin >> n >> k;
	cin >> g[0] >> g[1] >> g[2];


	int ans = 0;
	for(int J=1<<20; J; J/=2){
		if(chk(ans+J) >= k) ans+=J;
	}
	cout << fixed << setprecision(10);

	if(ans){
		cout << sqrt(ans) << '\n';
	}
	else{
		cout << -1 << '\n';
	}

}