Elina is reading a book written by Rujia Liu, which introduces a strange way to express non-negative integers. The way is described as following: Choose k different positive integers a1, a2, …, ak. For some non-negative m, divide it by every ai (1 ≤ i ≤ k) to find the remainder ri. If a1, a2, …, ak are properly chosen, m can be determined, then the pairs (ai, ri) can be used to express m. “It is easy to calculate the pairs from m, ” said Elina. “But how can I find m from the pairs?” Since Elina is new to programming, this problem is too difficult for her. Can you help her?
The input contains multiple test cases. Each test cases consists of some lines. Line 1: Contains the integer k. Lines 2 ~ k + 1: Each contains a pair of integers ai, ri (1 ≤ i ≤ k).
Output the non-negative integer m on a separate line for each test case. If there are multiple possible values, output the smallest one. If there are no possible values, output -1.
2 8 7 11 9
31
中国剩余定理： 能求解什么问题呢？ 问题： 一堆物品 3个3个分剩2个 5个5个分剩3个 7个7个分剩2个 问这个物品有多少个? 模线性方程组 设总数为n，则n%3=2,n%5=3,n%7=2;
m
