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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 1e9+7;

vector<ld> dp[2];

int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    //random_start();
    int n,t;
    cin >> n >> t;
    dp[0].resize(n*2+3,0);
    dp[1].resize(n*2+3,0);
    vector<ld> p = {1};
    rep(i,n)
    {
        ld x;
        cin >> x;
        p.pb(x);
    }
    sort(all(p));
    reverse(all(p));
    ld ans = 0;
    dp[0][n] = 1;
    rep2(i,1,n)
    {
        rep2(d,-i,i)
        {
            dp[1][d+n] = dp[0][d-1+n] * p[i] + dp[0][d+1+n] * (1 - p[i]);
        }
        ld sum = 0;
        rep2(d,-i,i)
        {
            if(d >= t)
            {
                sum += dp[1][d+n];
            }
        }
        rep2(d,-i,i)
        {
            swap(dp[1][d+n],dp[0][n+d]);
        }
       // cout << fixed << setprecision(10) << sum << " " << i-1 << " pref\n"; 
        ans = max(ans,sum);
    }
    cout << fixed << setprecision(10) << ans << "\n";
}