#include <cstdio>
#define w{fscanf(f,"%d",&x);while(p<=u && x<=q[u][0])u--;q[++u][0]=x;q[u][1]=i;}
int q[5000010][2],p,u=-1;
int main()
{
    int n,k,i,x;
    long long s;
    FILE *f=fopen("deque.in","r");
    fscanf(f,"%d%d",&n,&k);
    for(i=1;i<=k;i++)w;
    s=q[p][0];
    for(i=k+1;i<=n;i++){
        if(q[p][1]<=i-k)p++;
        w;
        s+=q[p][0];}
    f=fopen("deque.out","w");
    fprintf(f,"%lld",s);
    return 0;
}