CF879A.Borya's Diagnosis

It seems that Borya is seriously sick. He is going visit n doctors to find out the exact diagnosis. Each of the doctors needs the information about all previous visits, so Borya has to visit them in the prescribed order (i.e. Borya should first visit doctor 1, then doctor 2, then doctor 3 and so on). Borya will get the information about his health from the last doctor.

Doctors have a strange working schedule. The doctor i goes to work on the s__i-th day and works every d__i day. So, he works on days s__i, s__i + d__i, s__i + 2_d__i_, ....

The doctor's appointment takes quite a long time, so Borya can not see more than one doctor per day. What is the minimum time he needs to visit all doctors?

看来博里亚病得不轻。他需要去拜访 $n$ 位医生，以确定确切的诊断结果。每位医生都需要了解之前所有就诊的信息，因此博里亚必须按规定的顺序依次就诊（即：先看第 1 位医生，再看第 2 位医生，然后是第 3 位医生，依此类推）。博里亚将从最后一位医生处获得关于自身健康状况的诊断结果。

医生们的作息时间十分特殊：第 $i$ 位医生从第 $s_i$ 天开始上班，之后每隔 $d_i$ 天工作一次。因此，他工作的日期为 $s_i,\ s_i + d_i,\ s_i + 2d_i,\ \dots$。

医生的问诊耗时很长，因此博里亚每天最多只能看一位医生。那么，他看完所有医生所需的最短时间是多少？

First line contains an integer n — number of doctors (1 ≤ n ≤ 1000).

Next n lines contain two numbers s__i and d__i (1 ≤ s__i, d__i ≤ 1000).

第一行包含一个整数 $n$ —— 医生的数量（$1 \leq n \leq 1000$）。

接下来的 $n$ 行，每行包含两个数 $s_i$ 和 $d_i$（$1 \leq s_i, d_i \leq 1000$）。

Output a single integer — the minimum day at which Borya can visit the last doctor.

输出一个整数——Borya 能够拜访最后一位医生的最早天数。

In the first sample case, Borya can visit all doctors on days 2, 3 and 4.

In the second sample case, Borya can visit all doctors on days 10 and 11.

在第一个样例中，Borya 可以在第 2、3 和 4 天拜访所有医生。

在第二个样例中，Borya 可以在第 10 和 11 天拜访所有医生。