CF763C.Timofey and remoduling

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题目描述

Little Timofey likes integers a lot. Unfortunately, he is very young and can't work with very big integers, so he does all the operations modulo his favorite prime mm . Also, Timofey likes to look for arithmetical progressions everywhere.

One of his birthday presents was a sequence of distinct integers a1,a2,...,ana_{1},a_{2},...,a_{n} . Timofey wants to know whether he can rearrange the elements of the sequence so that is will be an arithmetical progression modulo mm , or not.

Arithmetical progression modulo mm of length nn with first element xx and difference dd is sequence of integers x,x+d,x+2d,...,x+(n1)dx,x+d,x+2d,...,x+(n-1)·d , each taken modulo mm .

输入格式

The first line contains two integers mm and nn ( 2<=m<=109+72<=m<=10^{9}+7 , 1<=n<=1051<=n<=10^{5} , mm is prime) — Timofey's favorite prime module and the length of the sequence.

The second line contains nn distinct integers a1,a2,...,ana_{1},a_{2},...,a_{n} ( 0<=a_{i}<m ) — the elements of the sequence.

输出格式

Print -1 if it is not possible to rearrange the elements of the sequence so that is will be an arithmetical progression modulo mm .

Otherwise, print two integers — the first element of the obtained progression xx ( 0<=x<m ) and its difference dd ( 0<=d<m ).

If there are multiple answers, print any of them.

输入输出样例

  • 输入#1

    17 5
    0 2 4 13 15
    

    输出#1

    13 2
    
  • 输入#2

    17 5
    0 2 4 13 14
    

    输出#2

    -1
    
  • 输入#3

    5 3
    1 2 3
    

    输出#3

    3 4
    
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