import sys
for line in sys.stdin:
a,b = map(int,line.split())
if a == b == 0:
break
else:
sum = a + b
print(sum)
难点在于记住多行输入的方式
import sys
for line in sys.stdin:

import sys
for line in sys.stdin:
a,b = map(int,line.split())
if a == b == 0:
break
else:
sum = a + b
print(sum)
难点在于记住多行输入的方式
import sys
for line in sys.stdin: