#include <iostream>
#include <cstdio>
#include <deque>
using namespace std;

int v[5000005];
deque < int > Q;
int front1=1,back1=0,n,k;
long long S;
void citire()
{

    scanf("%d%d",&n,&k);
    for(int i=1;i<=n;i++)
    {
        scanf("%d",&v[i]);
    }
    Q.push_front(1);
    for(int i=2;i<=n;i++)
    {
        if(Q.front()==i-k)
            Q.pop_front();
        while(v[i]<=v[Q.back()]&&!Q.empty())
            Q.pop_back();
        Q.push_back(i);
        if(i>=k)
        S+=v[Q.front()];
    }
    printf("%lld",S);
}
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    citire();
    //cout << "Hello world!" << endl;
    return 0;
}