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## 문제

An election was held today. A total of $n$ parties, numbered $1$ through $n$, has participated in this election, and $m$ slots were distributed among the parties based on the number of votes each party got. The following algorithm was used for slot distribution:

Suppose that the parties $1, 2, \ldots, n$ got $c_1, c_2, \ldots, c_n$ votes, respectively. Let $s = c_1 + c_2 + \ldots + c_n$. First, for each $i$, $\lfloor \frac{c_i}{s} \cdot m \rfloor$ slots are distributed to the party $i$. Then, the remaining slots are distributed from the parties with the larger value of the fractional part of $\frac{c_i}{s} \cdot m$, one slot per party. In case of a tie, the lower-indexed party has the priority.

You have the following information:

• The parties $1, 2, \ldots, n$ got exactly $a_1, a_2, \ldots, a_n$ votes, respectively.
• The parties $1, 2, \ldots, n$ got at least $b_1, b_2, \ldots, b_n$ slots, respectively.

Compute the minimum possible number of total slots $m$.

## 입력

The first line of input contains one integer $n$ ($1 \le n \le 100$). Then $n$ lines follow, each contains a pair of integers $a_i$ and $b_i$ ($1 \le a_i \le 1000$, $0 \le b_i \le 10^9$). You may assume that there exists at least one $i$ such that $b_i \ge 1$.

## 출력

Print the minimum possible number of total slots $m$.

## 예제 입력 1

3
1 2
4 5
2 3


## 예제 출력 1

11


## 예제 입력 2

4
1 0
6 5
4 4
5 8


## 예제 출력 2

25


## 예제 입력 3

1
42 42


## 예제 출력 3

42