N,M=map(int,input().split())
A=list(map(int,input().split()))


LIST=[]
for i in range(1,len(A)):
    LIST.append((A[i]-A[i-1]-1,1))

ANS=M

while LIST:
    if LIST[-1][0]<=1:
        LIST.pop()
    elif LIST[-1][0]%2==0:
        LIST.pop()
    else:
        k=LIST[-1][0]
        ko=LIST[-1][1]
        
        ANS+=1*ko
        LIST.pop()

        l=k//2
        LIST.append((l,ko*2))

print(N-ANS)