1-2+3。。。+99

# -*- coding:utf-8 -*-

m = 1
a = 0
b = 0
while m < 100:
   n = m%2
   if n == 0:
      a = a - m
   elif n == 1:
      b = b + m
   m = m + 1
sum = a + b
print(sum)


t = 0
for s in range(0,100):
   w = s%2
   if w == 0 :
      t = t - s
   elif w == 1 :
      t = t + s
print(t)