#include <cstdio>

using namespace std;

int v[5000010],n,k,q[5000010],s;

int main()
{
    FILE *f=fopen("deque.in","r");
    fscanf(f,"%d%d",&n,&k);
    int i;
    for(i=1;i<=n;i++)
        fscanf(f,"%d",&v[i]);
    int cap=1,coada=0;
    for(i=1;i<=n;i++)
    {
        while(cap<=coada && v[i]<=v[q[coada]]) coada--;
        q[++coada]=i;
        if(q[cap]==i-k) cap++;
        if(i>=k) s+=v[q[cap]];
    }
    fclose(f);
    f=fopen("deque.out","w");
    fprintf(f,"%d",s);
    return 0;
}