can you understand why this code prints None?

[arcbal]

# assuming n is always greater than m
def fd(n,m):
    if n%m==0:
        print(m)
        return m
    else:
        print(n,m)
        fd(n,(m-1))
print(fd(6,5))

the result is not what i expect,i expect

Output:
6,5
6,4
3
3

but the result i get is:

Output:
6,5
6,4
3
None

i don't why this None is occurring??