#include <bits/stdc++.h>
using namespace std ;
#define FAST ios_base::sync_with_stdio(false),cin.tie(nullptr),cout.tie(nullptr);
#define maxn 5000010

int n,i,k ;
int v[maxn],q[maxn] ;
long long int s ;
int front,back ;
int main()
{
    freopen("deque.in","r",stdin) ;
    freopen("deque.out","w",stdout) ;

    scanf("%d %d",&n,&k) ;
    for(i=1; i<=n; ++i)
    {
        scanf("%d",&v[i]) ;
    }
    front=1,back=0 ;
    for(i=1; i<=n; ++i)
    {

        while(front<=back && v[i]<=v[q[back]])
            back-- ;
        q[++back]=i ;
        if(q[front]==i-k)
            front++ ;
        if(i>=k)
            s+=v[q[front]];
    }
    printf("%lld\n",s) ;
    return 0 ;
}