#include <iostream>
#include <fstream>
using namespace std;
int main()
{
    ifstream f("deque.in");
    ofstream g("deque.out");
    int n,k,i,j,x=0,min;
    int v[500000];
    long long s=0;
    f>>n;
    f>>k;
    for(i=1;i<=n;i++)
        f>>v[i];
    while (x<=n-k)
    {
        min=v[x+1];
    for(j=1+x;j<=k+x;j++)
        {
        if (v[j]<min)
    {
        min=v[j];}

}
x++;
s=s+min;

}
g<<s;
}