#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
ifstream f("dezastru.in");
ofstream g("dezastru.out");
unsigned long long prod=0;
double a[30][30],b[30],sol;
int i,n,k,j,m,t;

int main()
{
f>>n>>m;
for (i=1;i<=n;i++)
    f>>a[1][i];
for (i=2;i<=m;i++)
{
    for (j=1;j<=n;j++)
    {
        b[j]=a[i-1][j];
    }
    for (j=i;j<=n;j++)
    {
        for (t=j-1;t>=1;t--) {prod++;a[i][j]=a[i][j]+b[j]*b[t];}
        cout<<a[i][j]<<" ";
    }
}
for (i=m;i<=n;i++) sol+=a[m][i];
g<<fixed<<setprecision(6)<<sol/prod;


    return 0;
}