/**
6 3
4 3 2 5 6 4
{idx,val}  idx -indice	val-cost
{0,0}
sol=4+0
it={1,4}
	push({1,4})
{0,0} {1,4}
sol=3+0=3
{2,3}
	pop({1,4})
	push({2,3})
{0,0} {2,3}
sol=2+0=2
	pop({2,3})
	push({3,2})
{0,0} {3,2}
sol=5+2
	pop({0,0})
{3,2} {4,7}
sol=6+2=8
{3,2}{4,7}{5,8}
sol=4+2
	pop({5,8})
	pop({4,7})
	push({6,6})
{3,2}{6,6}
*/
// Popa Bogdan Ioan, Colegiul National Aurel Vlaicu Orastie, clasa a 10-a
#include <bits/stdc++.h>
#define ll long long
using namespace std;
ifstream fin("zen.in");
ofstream fout("zen.out");
struct Zen
{
    int idx;
    ll val;
};
deque<Zen>DQ;
int n,K;
ll sol;
int val;
int i;
void update(ll val, int idx)
{
    Zen it={idx,val};
    while(!DQ.empty() && DQ.back().val>=it.val)
        DQ.pop_back();
    DQ.push_back(it);
}
ll query(int idx)
{
    if(idx>K)
        if(DQ.front().idx<idx-K)
            DQ.pop_front();
    return DQ.front().val;
}
int main()
{
    fin>>n>>K;
    DQ.push_back({0,0});
    for(i=1;i<=n;i++)
    {
        fin>>val;
        sol=val+query(i);
        update(sol,i);
    }
    fout<<sol<<"\n";
    return 0;
}