#include<bits/stdc++.h>
using namespace std;
deque<int>d;
long long s;
int i,n,a[5000010],k;
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",&a[i]);
    }
    for(i=1;i<=n;i++)
    {
        while(!d.empty()&&a[d.back()]>=a[i])
            if(d.size()==0)break;
            else d.pop_back();
        d.push_back(i);
        if(i-d.front()==k)d.pop_front();
        if(i>=k) s=s+a[d.front()];
    }
    printf("%lld",s);
    return 0;
}