LCM with recursion ( least common multiple)

[foxman322]

When i run this code python shell shows nothing

in '2.txt' 2 numbers " 21,53"

# least common multiple
def lcm(a,b):
 with open('2.txt') as f:
    a, b = [int(x) for x in next(f).split(',')]
    array = [[int(x) for x in line.split(',')] for line in f]
    m = a*b
    while a != 0 and b != 0:
        if a > b:
            a %= b
        else:
            b %= a
    return m // (a+b)

 print("a=%d ; b=%d ; LCM=%d"%(a,b,lcm(a, b)))