Linear Sequence
Statement
Goal
Information of linear sequence:A linear sequence is a number pattern that increases or decreases by the same amount each time. (From BBC Bitesize: https://www.bbc.co.uk/bitesize/guides/z7j2pv4/revision/)
You can find the formula of the nth term of the sequence by this formula:
formula of the nth term = first term of the sequence + (n - 1) * common difference
(There's a quicker way to do it :) )
Task:
You will be given four integers on separated lines. If the four integers have the same difference, it is a linear sequence. For example, (2, 4, 6, 8) is a linear sequence as they have the common difference of 2
You will need to find the formula to find the nth term of the sequence, in the form of (
In this task, b and c will not be zero. For example, there will be no 4n+0 or 0n+8. However, b can be -1 or 1 so you will need to simplify the formula to -n and n respectively (not -1n or 1n).
A little conclusion about what I mentioned in the last paragraph, c can be any integer, positive or negative:
1n+c => n+c
-1n+c => -n+c
Notes: If the numbers provided are not a linear sequence, output
Input
a, b, c and d: integers, each on a separate line.
Output
Line 1: Output a formula in the form of bn+c or ERROR
Constraints
-100 < a, b, c and d < 5201315
b and c are always integers.
b and c are always integers.
Example
Input
15 20 25 30
Output
5n+10
Game modes
Fastest, Shortest, Reverse
Test cases
Example Test
Input
15
20
25
30
Output
5n+10
Validator 1 Validator
Input
10
19
28
37
Output
9n+1
Bigger Number, both b and c are positive. Test
Input
32
43
54
65
Output
11n+21
Validator 2 Validator
Input
35
40
45
50
Output
5n+30
b is negative Test
Input
65
50
35
20
Output
-15n+80
Validator 3 Validator
Input
32
28
24
20
Output
-4n+36
c is negative Test
Input
-8
-4
0
4
Output
4n-12
Validator 4 Validator
Input
-9
-5
-1
3
Output
4n-13
both b and c are negative Test
Input
-9
-10
-11
-12
Output
-n-8
Validator 5 Validator
Input
-32
-38
-44
-50
Output
-6n-26
b is 1 Test
Input
10
11
12
13
Output
n+9
Validator 6 Validator
Input
3
4
5
6
Output
n+2
b is -1 Test
Input
6
5
4
3
Output
-n+7
Validator 7 Validator
Input
-9
-10
-11
-12
Output
-n-8
ERROR Test
Input
69
420
5201314
69
Output
ERROR
Validator 8 Validator
Input
8
9
5
6
Output
ERROR
Solution language
Solution
Stub generator input