# Practice on Toph

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# 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:

a1, a2, a3,………………..an

This is an arithmetic sequence if ai-ai+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 nth term. Otherwise you must print “Error”.

## Input

In First line there will be an integer T denoting number of test cases. Each of the case will contain 4 integers a1, a2, a3 and n.

Constraints:

• 1 ≤ T ≤ 100
• -300 ≤ a1, a2, a3 ≤ 300
• 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```

Discussion
Statistics

76% Solution Ratio

probal25Earliest, Nov '16

Ashik1233Fastest, 0.0s

Mohaimin66Lightest, 0 B

touhidurShortest, 125B

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