#include <iostream>
#include <fstream>

using namespace std;


int main(){


ifstream in("deque.in)");
ofstream out("deque.out)");

int n,k,v[5000],contor=0,min;
in  >>  n   >>  k;
long long sum=0;
in >> v[0];
min = v[0];
for(int i = 1 ;i<k;i++)
{
    in >> v[i];
    if(min>v[i])
        min = v[i];
}
sum += min;
for(int i = 0;i< n-k;i++){
    if(contor == k)
        contor = 0;
    in >> v[contor];
    min = v[0];
    for(int j = 1 ;j<k;j++)
    {
        if(min>v[j])
            min = v[j];
    }
    sum += min;
    contor ++;
}


out << sum;

in.close();
out.close();
return 0;
}