Arithmetic Progression Subsequences (2)

Write a program that reads an integer $n>1$ followed by a sequence of integers, and finds out whether the sequence contains a consecutive subsequence of length $n$ that forms an arithmetic progression.

A consecutive subsequence of integers forms an arithmetic progression if the difference between two consecutive numbers equals a fixed integer value $r$ . For instance, $4 5 6 7$ is an arithmetic progression with $r = 1$ , and $22 33 44 55 66$ is an arithmetic progression with $r = 11$ .

If the input sequence contains such a progression, the program must report the start number and the value $r$ . Otherwise, the program must indicate "No arithmetic progression of length n found".

Input

The input is an integer $n>1$ , followed by a sequence of integers containing at least 2 elements.

Output

If a progression subsequence of length $n$ exists, the output is the first element of the subsequence and the value of $r$ . Otherwise, the output is "No arithmetic progression of length n found".

Problem information

Author: ProAl

Generation: 2026-01-25T16:57:37.367Z