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/*
 * Opis: Główny nagłówek
 */
#include<bits/stdc++.h>
using namespace std;
using LL=long long;
using D=long double;
#define FOR(i,l,r)for(int i=(l);i<=(r);++i)
#define REP(i,n)FOR(i,0,(n)-1)
#define ssize(x)int(x.size())
#ifdef DEBUG
auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";}
#define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X)
#else
#define debug(...){}
#endif

constexpr int W = 2000;
constexpr int N = 5e4;


void generate_example(int& n, int& t, vector<D>& arr) {
	n = N;
	t = N / 2;
	arr.resize(n, 1./2);
}

int main() {
	cin.tie(0)->sync_with_stdio(0);
	int n, t;
	//vector<D> arr;
//	generate_example(n, t, arr);
	cin >> n >> t;
	vector<D> arr(n);
	for (auto& v : arr) {
		cin >> v;
	}
	sort(arr.begin(), arr.end());
	reverse(arr.begin(), arr.end());

	D res = 0;
	D mid = 0;
	vector<pair<int, D>> dp, temp; // every 2
	dp.reserve(4*W);
	temp.reserve(4*W);
	dp.push_back({0, 1});
	for (D p: arr) {
		D q = 1-p;
		mid += 2*p - 1;
		temp.push_back(dp.front());
		temp.front().first--;
		temp.front().second *= q;
		temp.resize(ssize(dp) + 1);
		FOR(i, 1, ssize(dp)-1) {
			temp[i].first = dp[i].first - 1;
			temp[i].second = p * dp[i-1].second + q * dp[i].second;
		}
		temp.back() = dp.back();
		temp.back().first++;
		temp.back().second *= p;

		D curr_res = 0;
		for (auto [wh, pr] : temp) {
			if (wh >= t) {
				curr_res += pr;
			}
		}
		res = max(res, curr_res);

		int mid_int = (int) mid;
		dp.clear();
		for (auto [wh, pr] : temp) {
			if (abs(wh - mid_int) <= W) {
				dp.push_back({wh, pr});
			}
		}
		temp.clear();
	}
	cout << fixed << setprecision(9) << res << "\n";
}