def isPowerOfTwo(n):
# return n > 0 and n&(n -1)==0
if n < 1:
return False
while n%2==0:
n = n // 2
return n==1
def isPowerOfTwo(n):
# return n > 0 and n&(n -1)==0
if n < 1:
return False
while n%2==0:
n = n // 2
return n==1