from heapq import heapify, heappop, heappush
N,K=map(int,input().split())
A=list(map(int,input().split()))
if N%2==1 and N//2+1<K:
    print("Impossible")
elif N//2<K:
    print("Impossible")
else:
    A=[-v for v in A]
    heapify(A)
    ANS=0
    for i in range(K*2-1):
        x = -heappop(A)
        if i%2==0:
            ANS+=x
    print(ANS)