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

if N%2==0:
    print(N*M)
    exit()
if N==1:
    print(0)
    exit()

A=[0]*min(50,N)

if len(A)%2==0:
    A.pop()

for i in range(33,-1,-1):
    A.sort()
    count=0

    for j in range(len(A)):
        if A[j]+(1<<i)<=M:
            count+=1

    for j in range(count//2*2):
        A[j]+=(1<<i)

ANS=(N-len(A))*M+sum(A)

print(ANS)