#include <iostream>
#include <cstdio>
#include <deque>
using namespace std;
deque <int>dq;
int n,k,i,a[5000003];
long long sum;
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]);
    dq.push_back(1);
    for(i=2;i<=n;i++)
    {
        while(!dq.empty() && a[dq.back()]>=a[i])
            dq.pop_back();
        dq.push_back(i);
        while(!dq.empty() && dq.front()<i-k+1)
            dq.pop_front();
        if(i>=k)
            sum+=a[dq.front()];
    }
    printf("%d",sum);
    return 0;
}