import bisect import copy import decimal import fractions import heapq import itertools import math import random import sys import time from collections import Counter,deque,defaultdict from functools import lru_cache,reduce from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max def _heappush_max(heap,item): heap.append(item) heapq._siftdown_max(heap, 0, len(heap)-1) def _heappushpop_max(heap, item): if heap and item < heap[0]: item, heap[0] = heap[0], item heapq._siftup_max(heap, 0) return item from math import gcd as GCD read=sys.stdin.read readline=sys.stdin.readline readlines=sys.stdin.readlines write=sys.stdout.write N,K=map(int,readline().split()) A=list(map(int,readline().split())) A1=[(A[i],-i) for i in range(1,N,2)] _heapify_max(A1) ans=0 min_i=N queue=[] while K and A1: a,i=_heappop_max(A1) i=-i while K and queue and queue[0]>=a: ans+=queue[0] _heappop_max(queue) K-=1 if K==0: break if i=a: ans+=queue[0] _heappop_max(queue) K-=1 while K: ans+=queue[0] _heappop_max(queue) K-=1 print(ans)