def reku(a,b):
    if a==b:
        return a
    elif (a%2==0 and b%2==0):
        return 2*reku(a//2,b//2)
    elif (a%2==1 and b%2==0):
        return reku(a,b//2)
    elif (a%2==0 and b%2==1):
        return reku(a//2,b)
    elif (a%2==1 and b%2==1 and a>b):
        return reku((a-b)//2, b)
    elif (a%2==1 and b%2==1 and a<b):
        return reku(a,(b-a)//2)