#include <stdio.h>

using namespace std;

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int minc,minci=0,v[500000],a,n,i,s=0,j,k;
    scanf("%i%i%i",&n,&k,&v[0]);
    minc=v[0];
    for(i=1; i<k; ++i)
    {
        scanf("%i",&v[i]);
        if(minc>v[i]) {minc=v[i];minci=i;}
    }
    s+=minc;
    while(i<n)
    {
        scanf("%i",&v[i]);
        if(minci>=i-k+1)
                    if(minci<v[i]) s+=minc;
                    else {minc=v[i];minci=i;s+=minc;}
        else {minc=v[i-k+1];minci=i-k+1;
            for(j=i-k+2;j<=i;++j)
                    if(v[j]<minc) {minc=v[j];minci=j;}
            s+=minc;
        }
        ++i;
    }
    printf("%i",s);
    return 0;
}