1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <cmath>

using namespace std;

int main() {
    int n, t;
    cin >> n >> t;
    
    vector<double> probabilities(n);
    for (int i = 0; i < n; ++i) {
        cin >> probabilities[i];
    }
    
    sort(probabilities.rbegin(), probabilities.rend());
    
    double result = 1.0;
    for (int i = 0; i < t; ++i) {
        result *= probabilities[i];
    }
    
    if (result < 1e-6) result = 0.0;
    
    cout << fixed << setprecision(20) << result << endl;
    
    return 0;
}