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//PROBLEM 2C
#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
const int D = 1000;

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int n, t;
    double ans = 0;
    cin >> n >> t;
    vector<double> P(n);
    for(auto &i : P) cin >> i;
    sort(all(P), greater<>());
    
    double expect = 0;
    int cur_L = floor(expect - D), cur_R = ceil(expect + D);
    vector<double> cur_dp(2*D + 10);//DP is prefix sum, currently have 0 with prob 1
    auto nxt_dp = cur_dp;
    for(int i = 0; i <= cur_R; i++) {
        cur_dp[i - cur_L] = 1;
    }
    auto get = [&](int i) -> double {
        if(i < cur_L) return 0;
        if(i > cur_R) return 1;
        return cur_dp[i - cur_L];
    };
    int total = 0;
    for(auto p : P) {
        total++;
        double q = 1. - p;
        expect += p;
        int nxt_L = floor(expect - D), nxt_R = ceil(expect + D);
        fill(all(nxt_dp), 0);
        for(int i = nxt_L; i <= nxt_R; i++) {
            nxt_dp[i - nxt_L] = get(i - 1) * p + get(i) * q;
        }

        swap(cur_dp, nxt_dp);
        cur_L = nxt_L, cur_R = nxt_R;
        int must_solve = (t + total + 1) / 2;
        ans = max(ans, 1. - get(must_solve - 1));
        // assert(cur_dp[0] < 1e-12 && (1 - cur_dp[cur_R - cur_L]) < 1e-12);
    }
    cout << fixed << setprecision(15) << ans << '\n';
}