my problem is a &= b
after searching internet for a while i found that its a bitwise and operator but cant figure out what its doing in this program

> 
> 
> ```
> x = int(input("Insert first number: "))
> y = int(input("Insert second number: "))
> 
> if x>y:
>     x,y =x,y
> elif x<y :
>     x,y= y,x
> 
> while x != 0 and y != 0:
>     if x > y:
>         x %= y
>     else:
>         y &= x
> 
> GCD = x + y
> print("The greatest common divisor = ",GCD)
> 
> ```
> 
>