N,M=map(int,input().split())
if N%2==0:
    print(N*M)
    exit()
if N==1:
    print(0)
    exit()
d = 2**(M.bit_length()-1)
ans = (N-1)*M

rest = M-d
for i in range(M.bit_length()-2,-1,-1):
    if (1<<i)&M==0 and rest - (1<<i) >=0:
        rest -= (1<<i)
        ans += (1<<i)*2
print(ans)