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#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n,t;
    cin>>n>>t;
    vector<long double> p(n);
    for(int i =0;i<n;i++)
    {
        cin>>p[i];
    }
    sort(p.begin(),p.end());
    reverse(p.begin(),p.end());
    int sn = floor(sqrt(n));
    vector<long double> pr(n*2+1);
    for(int i = 0;i<n*2+1;i++)
    {
        pr[i] = 0;
    }
    pr[n] = 1;
    long double ans = 0;
    for(int i = 0;i<n;i++)
    {
        long double cans = 0;
        vector<long double> cu(n*2+1);
        for(int j = 0;j<2*n+1;j++)
        {
            cu[j] = 0;
        }
        for(int j = 0;j<2*n+1;j++)
        {
            if(pr[j] != 0)
            {
                cu[j+1] += pr[j] * p[i];
                cu[j-1] += pr[j] * (1 - p[i]);
            }
        }
        pr = cu;
        for(int j = n+t ;j<2*n+1;j++)
        {
            cans+=pr[j];
        }
        ans = max(ans,cans);
    }
    cout<<fixed<<setprecision(8)<<ans<<"\n";
}