#include <algorithm>
#include <cstdio>
#include <cmath>

constexpr int MAXN = 2000 + 2;
constexpr long double DINF = 1e16;

int s[MAXN];

long double f[MAXN][MAXN];

int main() {
    int n, m;
    scanf("%d%d", &n, &m);

    for (int i = 1; i <= n; i ++) {
        scanf("%d", &s[i]);

        f[0][i] = DINF;
    }

    std::sort(s + 1, s + n + 1);

    f[0][0] = 0;

    for (int i = 1; i <= n; i ++) {
        for (int j = i; j <= n; j ++) {
            long long sum = 0;

            f[i][j] = DINF;

            for (int k = j; k >= i; k --) {
                f[i][j] = std::min(
                  f[i][j],
                  f[i - 1][k - 1] + sqrtl((sum += s[k]) * (j - k + 1))
                );
            }
        }
    }

    printf("%.15Lf\n", f[m][n]);

    return 0;
}