Unable to return a variable from a function, when the function is called inside the same function. Programming Language: Python

Question

def m():
    m1 = input()
    m1.lower()
    if m1 in [\'a\', \'b\', \'c\', \'d\', \'e\', \'f\', \'g\', \'h\', \'i\']:
        return m1
    else:
        m()
f= m()