https://zerojudge.tw/ShowProblem?problemid=a012
https://onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=996
X
too EZ 絕對值abs()。
while True:
try:
first, second = map(int, input().split())
print(abs(first - second))
except:
break