#include<stdio.h>
int v[5000001];
long long s;
int main(){
    int i,l,j,k,n,min;
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    min=10000001;
    for(i=1;i<=n;i++){

        scanf("%d",&v[i]);
        if(i<=k){
            if(min>v[i])
                min=v[i];
        }
    }
    s=min;
    for(i=1,j=k+1;j<=n;j++,i++){
        if(min==v[i]){
            min=10000001;
            for(l=i+1;l<=i+k;l++)
                if(min>v[l])
                    min=v[l];
        }
        else
            if(min>v[j])
                min=v[j];
        s+=min;
    }
    printf("%I64d",s);

    return 0;
}