the idea is really simple :) the binary of power of fours have only one 1 and the 1 is in the odd position of the binary. ex: bin(4^0)=1 (has only one 1 and the 1 is in an odd position), bin(4^1)=100 (has only one 1 and the 1 is in an odd position). Same can be said about all the power of fours.

In this code, Ive a counter to count the number of 1's in binary, and have a flag to see where the 1 occurs. The flag is set if the 1 is in a odd position.

For the num to be a power of four, the counter must equal 1 and flag must equal True

```
class Solution(object):
def isPowerOfFour(self, num):
"""
:type num: int
:rtype: bool
"""
if num<0:
return False
count=0
oddFlag=False
i=3
while num!=0:
if num&1==1:
count+=1
if i%2==1:
oddFlag=True
num>>=1
i+=1
if count==1 and oddFlag==True:
return True
return False
```