#include <iostream>
#include <set>
#include <string>
#include <sstream>


using namespace std;


class cable {
public:
	cable(int length) {
		this->length = length;
		criticalLength = length;
		pieces = 0;
	}
	int length;
	int pieces;
	int criticalLength;
	bool operator <(const cable& c) const {
		return criticalLength > c.criticalLength;
	}
	void breakCable() {
		pieces++;
		criticalLength = length / (pieces + 1);
		/*cout << "l=" << length << 
			", al=" << length/pieces << " cl=" << criticalLength << ", p=" << pieces << endl;*/
	}
	int actualLength() {
		return length / pieces;
	}	
};

int parseLength(string length) {
	int l = length.length();
	istringstream is(length.substr(0, l-3) + length.substr(l-2));
	int t;
	is >> t;
	return t;
}

int doit(int cables, int pieces) {
	typedef multiset<cable> tq;
	tq queue;
	for (int i=0; i<cables; ++i) {
		string length;
		cin >> length;
		queue.insert(cable(parseLength(length)));
	}
	int currentPieces = 0;
	while (true) {
		tq::iterator head = queue.begin();
		cable c = *head;
		queue.erase(head);
		c.breakCable();
		if (c.criticalLength == 0)
			return 0;
		currentPieces++;
		if (currentPieces == pieces)
			return c.actualLength();
		queue.insert(c);
	}
}

string format(int number) {
	ostringstream s;
	s << number;
	string r = s.str();
	while (r.length() < 3) r = "0" + r;
	int l = r.length();
	return r.substr(0, l-2) + "." + r.substr(l-2);
}

int main() {
	int cables, pieces;
	while (1) {
		cin >> cables >> pieces;
		if (cables == 0 && pieces == 0)
			break;
		cout << format(doit(cables, pieces)) << endl;
	}
	return 0;
}