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;
using System.Text;
using System.Threading.Tasks;

namespace AtCoder.ABC118
{
    class D
    {
        public static void Solve()
        {
            var s = Console.ReadLine().Split(' ');
            var a = Console.ReadLine().Split(' ')
                .Select(x => int.Parse(x)-1)
                .OrderByDescending(x => x)
                .ToArray();
            int n = int.Parse(s[0]);
            int m = int.Parse(s[1]);
            int[] dp = Enumerable.Repeat(0,n+1).ToArray();
            int[] cost = { 2, 5, 5, 4, 5, 6, 3, 7, 6 };

            for (int i = 0; i < m; i++)
            {
                dp[n - cost[a[i]]] = 1;
            }

            for(int i = n; 1 < i; i--)
            {
                if (dp[i] <= 0)
                    continue;

                for(int j = 0; j < m; j++)
                {
                    var nc = i - cost[a[j]];
                    if (nc < 0)
                        continue;
                    dp[nc] = dp[i] + 1;
                }
            }
            //Console.WriteLine(dp[0]);

            var c = 0;
            while (c != n)
            {
                for(int i = 0; i < m; i++)
                {
                    int nc = c + cost[a[i]];

                    if (n < nc)
                        continue;

                    if (dp[c] == dp[nc]+1)
                    {
                        if (dp[c] == 1 && nc != n)
                            continue;

                        Console.Write(a[i] + 1);
                        c = nc;
                        break;
                    }
                }
            }
            Console.Write('\n');
        }
    }
}
namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            ABC118.D.Solve();
        }
    }
}