First Presence of an Opposite Pair

Write a program that receives on stdin lines containing integers and writes out the first line in which both some number and its opposite appear; the line is to be reported together with the number itself.

Input

The input is a sequence of zero or more lines. Each line cointains zero or more integers, separated by spaces.

Output

Output is the first line of the input in which both some number $n$ and its opposite $-n$ appear, preceded by the non-negative case of the number itself, with ": " (colon-single space) as separator. If several such numbers appear, the earliest-starting pair is to be reported. If there is no such line, the program must write "Not found."

Problem information

Author: José Luis Balcázar

Generation: 2026-01-25T17:02:55.092Z