CF1879A.Rigged!

Monocarp organizes a weightlifting competition. There are $n$ athletes participating in the competition, the $i$-th athlete has strength $s_i$ and endurance $e_i$. The $1$-st athlete is Monocarp's friend Polycarp, and Monocarp really wants Polycarp to win.

The competition will be conducted as follows. The jury will choose a positive (greater than zero) integer $w$, which denotes the weight of the barbell that will be used in the competition. The goal for each athlete is to lift the barbell as many times as possible. The athlete who lifts the barbell the most amount of times will be declared the winner (if there are multiple such athletes — there's no winner).

If the barbell's weight $w$ is strictly greater than the strength of the $i$-th athlete $s_i$, then the $i$-th athlete will be unable to lift the barbell even one single time. Otherwise, the $i$-th athlete will be able to lift the barbell, and the number of times he does it will be equal to his endurance $e_i$.

For example, suppose there are $4$ athletes with parameters $s_1 = 7, e_1 = 4$; $s_2 = 9, e_2 = 3$; $s_3 = 4, e_3 = 6$; $s_4 = 2, e_4 = 2$. If the weight of the barbell is $5$, then:

• the first athlete will be able to lift the barbell $4$ times;
• the second athlete will be able to lift the barbell $3$ times;
• the third athlete will be unable to lift the barbell;
• the fourth athlete will be unable to lift the barbell.

Monocarp wants to choose $w$ in such a way that Polycarp (the $1$-st athlete) wins the competition. Help him to choose the value of $w$, or report that it is impossible.

Monocarp 正在组织一场举重比赛。共有 $n$ 名运动员参加该比赛，其中第 $i$ 名运动员的力量为 $s_i$，耐力为 $e_i$。第 $1$ 名运动员是 Monocarp 的朋友 Polycarp，而 Monocarp 非常希望 Polycarp 获胜。

比赛将按如下方式进行：裁判将选定一个正整数 $w$（即比赛中所用杠铃的重量）。每名运动员的目标是尽可能多次地举起该杠铃。举起次数最多的运动员将被宣布为冠军（若存在多名运动员并列最多，则无人获胜）。

若杠铃重量 $w$ 严格大于 第 $i$ 名运动员的力量 $s_i$，则第 $i$ 名运动员甚至无法举起杠铃一次；否则，第 $i$ 名运动员可以举起杠铃，且其举起次数等于其耐力 $e_i$。

例如，假设有 $4$ 名运动员，参数分别为 $s_1 = 7, e_1 = 4$；$s_2 = 9, e_2 = 3$；$s_3 = 4, e_3 = 6$；$s_4 = 2, e_4 = 2$。若杠铃重量为 $5$，则：

• 第一名运动员可举起杠铃 $4$ 次；
• 第二名运动员可举起杠铃 $3$ 次；
• 第三名运动员无法举起杠铃；
• 第四名运动员无法举起杠铃。

Monocarp 希望选择一个 $w$，使得 Polycarp（即第 $1$ 名运动员）赢得比赛。请帮助他确定这样的 $w$ 的值；若不可能，请报告无法实现。

The first line contains one integer $t$ ($1 \le t \le 100$) — the number of test cases.

The first line of each test case contains one integer $n$ ($2 \le n \le 100$) — the number of athletes. Then $n$ lines follow, the $i$-th of them contains two integers $s_i$ and $e_i$ ($1 \le s_i \le 10^9$; $1 \le e_i \le 100$) — the strength and the endurance of the $i$-th athlete.

第一行包含一个整数 $t$（$1 \le t \le 100$）—— 测试用例的数量。

每个测试用例的第一行包含一个整数 $n$（$2 \le n \le 100$）—— 运动员的数量。随后是 $n$ 行，其中第 $i$ 行包含两个整数 $s_i$ 和 $e_i$（$1 \le s_i \le 10^9$；$1 \le e_i \le 100$）—— 分别表示第 $i$ 位运动员的力量和耐力。

For each test case, print the answer as follows:

• if the answer exists, print one integer — the value of $w$ meeting the constraints. The integer you print should satisfy $1 \le w \le 10^9$. It can be shown that if the answer exists, at least one such value of $w$ exists as well. If there are multiple answers, you can print any of them;
• otherwise, print one integer $-1$.

对于每个测试用例，请按如下方式输出答案：

• 如果答案存在，则输出一个整数——满足约束条件的 $w$ 的值。您输出的整数应满足 $1 \le w \le 10^9$。可以证明：若答案存在，则至少存在一个满足该范围的 $w$ 值。若存在多个答案，您可以输出其中任意一个；
• 否则，输出一个整数 $-1$。

The first test case of the example is described in the statement.

示例的第一个测试用例已在题目描述中说明。