N,M=map(int, input().split())
if N==1:
  print(0)
  exit()
  
if N%2==0:
  print(M*N)
  exit()
  
ans=(N-1)*M
A=[]
for i in range(30):
  A.append(M%2)
  M//=2

cnt=0
for i in range(29,-1,-1):
  if A[i]==1:
    cnt+=1
  elif cnt>1:
    ans+=pow(2,i+1)
print(ans)