python小学堂1

sun=0
start=1
while True:
    start1=start%2
    if start1==1:
        sun = start + sun
    elif start1==0:
        sun=sun-start
    if start==100:
        break
    start += 1
print(sun)

 sun=0
 start=1
 while True:
     start1=start%2
     if start1==1:
         sun = start + sun
     elif start1==0:
         sun=sun-start
     if start==100:
         break
     start += 1
 print(sun)

sun=0
start=1
while True:
    start1=start%2
    if start1==1:
        sun = start + sun
    elif start1==0:
        sun=sun-start
    if start==100:
        break
    start += 1
print(sun)

 sun=0
 start=1
 while True:
     start1=start%2
     if start1==1:
         sun = start + sun
     elif start1==0:
         sun=sun-start
     if start==100:
         break
     start += 1
 print(sun)