Range bitwise and

class Solution:
    def rangeBitwiseAnd(self, left: int, right: int) -> int:
        steps=0
        while left!=right:
            steps+=1
            left=left>>1
            right=right>>1
        return left<<steps
```
The idea is very simple:

1.last bit of (odd number & even number) is 0.
2.when m != n, There is at least an odd number and an even number, so the last bit position result is 0.
3.Move m and n rigth a position.
Keep doing step 1,2,3 until m equal to n, use a factor to record the iteration time.
return left<<steps because left reaches to 0 early then right while doing right shift operations


```