I've solved the psuedocode , but the thing is I am not able to find the solution if the loop never ends {i.e., -1 . Its a bit tricky}.

If any one can find the solution please do reply back.

def iterateIt(a):
    emp = []
    rep = 0

    while True:
        b = []
        for x in a:
            for y in a:
                if x != y:
                    temp = abs(x-y)
                    b.append(temp)
        a = b
        rep = rep + 1

        if a == emp:
            return rep