#include <fstream>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
unsigned n,k,i,j;
int a[101],s,minim=10000;
int main()
{
    fin>>n>>k;
    for(i=1;i<=n;i++)
        fin>>a[i];
    for(i=1;i<=n-k+1;i++)
    {
        minim=10000;
        for(j=i;j<i+k;j++)
            {
                if(a[j]<minim)
                    minim=a[j];
            }
            s=s+minim;
    }
    fout<<s;
    return 0;
}