Planning Production

Before starting each product, cash must be at least its worst-case cost w, but only its expected cost e is actually deducted. Production can be arranged in any order; find the minimum initial cash needed to complete all products.

输入格式

The first line contains n, followed by n lines of w e. Complete original bounds: 1≤n≤100000, 1≤e≤w≤100000. Output an exact integer, not limited to 32 bits by the int in the original example signature.

输出格式

Output a single integer answer.

样例 1

输入：

2
5 1
4 3

输出：

5

样例 2

输入：

2
5 5
5 5

输出：

10

样例 3

输入：

1
1 1

输出：

1

样例说明

The outputs of the three public examples are, in order: 5; 10; 1. Verified by independent enumeration or direct simulation.