Alice and Bob.txt

Description
Alice lives in village A and Bob lives in village B. They love jogging very much. Every morning they start jogging at the same time, head for the other's village and then, when arrive, immediately turn round, and jog back to their own villages.
This morning, Alice noticed when she met Bob for the first time, they were m meters away from A, and when she arrived at B, turned round, jogged back and met Bob from the oposite for the second time, they were n meters away from B.
Alice told it to Bob and asked him to calculate the distance from A to B. Bob was puzzled. Can you help him?
Input
Multiple test cases. Two integer m, n in a line for each case. A line containing "0 0" indicates end of input.
Output
One integer in a line for each test case : distance from A to B.
Sample Input
400 200
0 0
Sample Output
1000