merge sort

#!/usr/bin/python3
import sys


def merge(p, q):
    s = []
    while 0 < len(p) and 0 < len(q):
        a = p[0]
        b = q[0]
        if a <= b:
            s.append(a)
            p.pop(0)
        else:
            s.append(b)
            q.pop(0)
    if 0 < len(p):
        s.extend(p)
    elif 0 < len(q):
        s.extend(q)
    return s


def mergesort(a):
    n = len(a)
    if n <= 1:
        return a
    return merge(mergesort(a[:n // 2]), mergesort(a[n // 2:]))


a = list(map(int, sys.argv[1:]))
print(a)
print(mergesort(a))