Problem

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A pair of neighboring elements with the same signs

Problem

You are given an array of integers. Write a program that determines if an array has a pair of adjacent elements with the same signs.


Input
First given number N — the number of elements in the array (1<=N<=10000). The  N numbers — array elements. The array consists of integers, each modulo no more than 100.

Imprint
Output the word YES if there is a pair of adjacent elements with the same signs. Otherwise, output the word NO.
 
Examples
# Input Output
1 5
1 -3 4 -2 1 		NO
 

time 1000 ms
memory 256 Mb
Rules for program design and list of errors in automatic problem checking

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