Problem:
Score : 100 points

Problem Statement

You are given positive integers A and B.

If A is a divisor of B, print A + B; otherwise, print B - A.

Constraints

All values in input are integers.

1 \leq A \leq B \leq 20

Input

Input is given from Standard Input in the following format:

A B

Output

If A is a divisor of B, print A + B; otherwise, print B - A.

Sample Input 1

4 12

Sample Output 1

16

As 4 is a divisor of 12, 4 + 12 = 16 should be printed.

Sample Input 2

8 20

Sample Output 2

12

Sample Input 3

1 1

Sample Output 3

2

1 is a divisor of 1.

Solution in C# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;

class Program{

  static int n = 0;
  static int ans = 0;

  static int Main() {

    n = int.Parse(Console.ReadLine());
    int[] a = new int[n];

    string[] nya = Console.ReadLine().Split(' ');
    for (int i = 0; i < n; i++) {
      a[i] = int.Parse(nya[i]);
    }
    // ここまで入力

    while(true){
      if (a.Max() == a.Min()) {
        ans = a.Min();
        break;
      }
      a = Noo(a);
      // if (a.Max() == a.Min()) {
      //   ans = a.Min();
      //   break;
      // }
    }

    // Console.WriteLine("min = {0}", ans);
    return ans;
  }


  static int[] Noo(int[] a) {

    int max = a.Max();
    int max2 = 0;

    for (int i = 0; i < a.Length; i++) {
      if (a[i] > max2) {
        if (a[i] != max) {
          max2 = a[i];
        }
      }
    }

    if (max % max2 == 0) {
      a[Array.IndexOf(a, max)] = max2;
    } else {
      a[Array.IndexOf(a, max)] = max % max2;
    }
    return a;

  }
}