#include <bits/stdc++.h>
#include <cstdio>
#include <deque>
using namespace std;

int n,i,k,a[5000005];
long long s;
deque<int>d;
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(!d.empty()&&a[d.back()]>=a[i])
            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;
}