day07_作业

#5. 求1-2+3-4+5 ... 99的所有数的和
sum=0
a=0
sum1=0
sum2=0
while a < 100:

    if a % 2 == 1:

        sum1 += a
    else:
        sum2 -= a

    a += 1

    sum= sum1 + sum2
print(sum)