#include <cstdio>
#include <deque>

using namespace std;

int a[5000005];
deque <int> d;

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int n,k,x;
    long long sol=0;
    scanf("%d%d",&n,&k);
    for(int i=1;i<=n;++i){
		scanf("%d",&x);
		a[i]=x;
    }
    for(int i=1;i<=n;++i){
    	while(!d.empty() && a[i]<=a[d.back()])
			d.pop_back();
		d.push_back(i);
		if(d.front()==i-k)
			d.pop_front();
		if(i>=k)
			sol+=a[d.front()];
    }
    printf("%lld",sol);
    return 0;
}