This code is throwing NZEC Runtime error. Please help.
def Change(elements, size):
if size in (0,1,2):
pass
elif size == 3:
elements[1],elements[2] = elements[2], elements[1]
else:
for j in range(1, size-2, 2):
elements[j], elements[j+1] = elements[j+1], elements[j]
def main():
tCases = int(raw_input().strip())
ans = []
for i in range(tCases):
size = int (raw_input().strip())
elements = map(int, raw_input().split(' '))
elements.sort()
Change(elements, size)
ans.append(elements)
for res in ans:
print res
if __name__ == '__main__':
main()