求1-2+3-4+5-6+……99的和

 1 #所有奇数的和
 2 a = 1
 3 s_a = 0
 4 while a < 100:
 5     if a % 2 != 0:
 6         s_a = s_a + a
 7     a = a + 1
 8 #所有偶数的和
 9 b = 2
10 s_b = 0
11 while b < 101:
12     if b % 2 == 0:
13         s_b = s_b + b
14     b = b + 1
15 #奇数的和减去偶数的和就是1-2+3-4+5-6……99的和
16 x = s_a - s_b
17 print(x)