#include<cstdio>
#include<deque>
using namespace std;
int n,k,i,a[5000004];
long long s;
deque<int>c;
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]);
        while(!c.empty()&&a[c.back()]>=a[i])c.pop_back();
        c.push_back(i);
        if(c.front()<=i-k)c.pop_front();
        if(i>=k)s=s+a[c.front()];
    }
    printf("%lld",s);
    return 0;
}