Challenges

In mathematics, an arithmetic progression (AP) or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant. John was writing an Arithmetic sequence with N terms, but while writing he mistakenly made one wrong entry and he is sure that first term is right. Help him to find the wrong term entered by him.

The first line of input contains a single line T, which represents the number of testcases. Then first line of each test case contains an integer N :Total number of terms. Then N space separated integers denoting the sequence.

For each test case. Print the wrongly entered term.

1<=T<=100. 4<=N<=1000. 1<=Terms<=1000.

2
5
1 3 5 6 9
4
1 2 3 5

6
5