#include <iostream>
#include <stdio.h>
#include <deque>

using namespace std;

const int N = 5000001;
const char inf[] = "deque.in";
const char outf[] = "deque.out";

int n,k,a[N];
long long s;
deque<int> q;

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