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#include <bits/stdc++.h>

#define ll long long
#define db double
#define fors(u, n, s) for(ll u = (s); u < (n); u++)
#define foru(u, n) fors(u, n, 0)
#define f first
#define s second
#define vec vector
#define pb push_back
#define ir(a, b, x) (((a) <= (x)) && ((x) <= (b)))

using namespace std;

const int N = 5e4 + 100;
int n, t;

const db eps = 1e-30;

db _dp[2*N];
db _dp_[2*N];

db* dp = _dp;
db* dp_ = _dp_;

int main() {
	cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
	cin >> n >> t;

	vec<db> ps;

	ps.resize(n);

	foru(i, n) {
		db x; cin >> x; ps[i]=x;
	}

	foru(i, n) ps[i] *= -1;
	sort(ps.begin(), ps.end());
	foru(i, n) ps[i] *= -1;

	int l = N;
	int r = N;

	dp[N] = 1;

	db ans = 0;

	if(t==0) ans = 1;

	for(auto p : ps){
		l --; r ++;
		fors(i, r+1, l) {dp_[i] = 0;}
		for(int i = l+1; i < r; i += 2) {
			dp_[i+1] += dp[i]*p;
			dp_[i-1] += dp[i]*(1-p);
		}

		swap(dp, dp_);

		db subans = 0;

		fors(i, r+1, max(N+t, l)) {
			subans += dp[i];
		}

		ans = max(ans, subans);

		while(dp[l] <= eps) l++;
		while(dp[r] <= eps) r--;
	}

	cout << fixed << setprecision(7);
	cout << ans;
	
    return 0;
}