Problem:
Score : 100 points

Problem Statement

You are given two integers A and B as the input. Output the value of A + B.

However, if A + B is 10 or greater, output error instead.

Constraints

A and B are integers.

1 ≤ A, B ≤ 9

Input

Input is given from Standard Input in the following format:

A B

Output

If A + B is 10 or greater, print the string error (case-sensitive); otherwise, print the value of A + B.

Sample Input 1

6 3

Sample Output 1

9

Sample Input 2

6 4

Sample Output 2

error

Solution in Ruby (2.3.3) (judge verdict: Runtime Error)

n,$a,$b=gets.split.map(&:to_i)
$h=(1..n).map{gets.to_i}
def calc(x)
  $h.select{|h|h>$b*x}
    .inject(0){|s,h|((h.to_f-$b*x)/($a-$b)).ceil+s}<=x
end
p (0..10**9).bsearch{|i|calc(i)}