Given n sticks. The ith stick has a length of ai, and there is a marked point on the stick located bi from one end (and ai−bi from the other end).
You need to arrange the n sticks parallel to each other such that there exists a straight line passing through all the marked points on the sticks, and this line is perpendicular to the sticks. Determine the maximum length that all the sticks can collectively cover.
**You can rotate the stick freely.**
For example, with two sticks (5,2) and (4,1), the maximum horizontal length they can cover is 6.
### Input
- The first line contains an integer n.
- The next n lines each contain two integers ai and bi.
### Output
- Print a single integer, the maximum length that can be covered.
### Constraints
- 1≤n≤105.
- 1≤ai,bi≤109.
### Example
Input:
25243
Output:
6
Input 2:
454535251
Output 2:
8
### Subtasks
- Subtask 1 (20 of the points): 1≤n,ai,bi≤10.
- Subtask 2 (20 of the points): 1≤n≤2.
- Subtask 3 (20 of the points): 1≤n≤1000.
- Subtask 4 (20 of the points): bi=0 for all 1≤i≤n.
- Subtask 5 (20 of the points): No additional constraints.