# Practice on Toph

Participate in exhilarating programming contests, solve unique algorithm and data structure challenges and be a part of an awesome community.

# An Arithmetic Problem

Limits 1s, 512 MB

A sequence is an arithmetic sequence if every two successive number has same difference. Suppose this is a sequence of numbers:

$a_1$, $a_2$, $a_3$, …, $a_n$

This is an arithmetic sequence if $a_i - a_{i+1}$ is same for each i from 1 to $n-1$.

You are given first 3 terms of a sequence and the value of $n$. If it is an arithmetic sequence you must print the $n$-th term. Otherwise you must print “Error”.

## Input

In the first line there will be an integer $T$ ($1 ≤ T ≤ 2000$) denoting number of test cases. Each of the case will contain 4 integers $a_1$, $a_2$, $a_3$ ($-300 ≤ a_1, a_2, a_3 ≤ 300$) and $n$ ($1 ≤ n ≤ 1000$).

## Output

In each line specify the case number and print the answer.

## Sample

InputOutput
3
1 2 3 10
1 4 3 10
15 30 45 5

Case 1: 10
Case 2: Error
Case 3: 75


### Statistics

79% Solution Ratio

rakeenEarliest, Aug '15

emrulk1Fastest, 0.0s

Mohaimin66Lightest, 0 B

bokaifShortest, 118B