Problem:
Problem A: Equal Total Scores

Taro and Hanako have numbers of cards in their hands.
Each of the cards has a score on it.
Taro and Hanako wish to make the total scores of their cards equal
by exchanging one card in one's hand with one card in the other's hand.
Which of the cards should be exchanged with which?

Note that they have to exchange their
cards even if they already have cards of the same total score.

Input

The input consists of a number of datasets.
Each dataset is formatted as follows.

n m

s1

s2

...

sn

sn+1

sn+2

...

sn+m

The first line of a dataset contains two numbers
n and m delimited by a space, where n
is the number of cards that Taro has
and m is the number of cards that Hanako has.
The subsequent n+m lines
list the score for each of the cards,
one score per line. The first n scores
(from s1 up to sn)
are the scores of Taro's cards
and the remaining m scores
(from sn+1 up to sn+m)
are Hanako's.

The numbers n and m
are positive integers no greater than 100. Each score
is a non-negative integer no greater than 100.

The end of the input is indicated by a line containing two zeros delimited
by a single space.

Output

For each dataset, output a single line containing two numbers delimited
by a single space, where the first number is the score of the card Taro
gives to Hanako and the second number is the score of the card Hanako gives
to Taro.
If there is more than one way to exchange a pair of cards
that makes the total scores equal,
output a pair of scores whose sum is the smallest.

In case no exchange can make the total scores equal, output a
single line containing solely -1.
The output must not contain any superfluous characters
that do not conform to the format.

Sample Input

2 2
1
5
3
7
6 5
3
9
5
2
3
3
12
2
7
3
5
4 5
10
0
3
8
1
9
6
0
6
7 4
1
1
2
1
2
1
4
2
3
4
3
2 3
1
1
2
2
2
0 0

Output for the Sample Input

1 3
3 5
-1
2 2
-1

Solution in C# (judge verdict: Accepted)

using System;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using StringBuilder = System.Text.StringBuilder;
//using System.Numerics;
using Number = System.Int64;
namespace Program
{
    public class Solver
    {
        public void Solve()
        {
            for (int n = sc.Integer(); n > 0; n = sc.Integer())
            {
                var m = sc.Integer();
                var a = sc.Integer(n);
                var b = sc.Integer(m);
                var A = a.Sum();
                var B = b.Sum();
                var sum = 1000000000;
                var p = -1;
                var q = -1;
                for (int i = 0; i < n; i++)
                    for (int j = 0; j < m; j++)
                    {
                        if (A - a[i] + b[j] == B - b[j] + a[i])
                        {
                            if (sum > a[i] + b[j])
                            {
                                sum = a[i] + b[j];
                                p = a[i];
                                q = b[j];
                            }
                        }
                    }
                if (sum < 1000000000)
                    IO.Printer.Out.WriteLine("{0} {1}", p, q);
                else IO.Printer.Out.WriteLine(-1);
            }
        }
        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());
        static T[] Enumerate<T>(int n, Func<int, T> f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}
#region main
static class Ex
{
    //static public string AsString(this IEnumerable<char> ie) { return new string(System.Linq.Enumerable.ToArray(ie)); }
    //static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
    static public void Main()
    {
        var solver = new Program.Solver();
        solver.Solve();
        Program.IO.Printer.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO
{
    using System.IO;
    using System.Text;
    using System.Globalization;
    public class Printer : StreamWriter
    {
        static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
        public static Printer Out { get; set; }
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
        public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
        public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
        public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
    }
    public class StreamScanner
    {
        public StreamScanner(Stream stream) { str = stream; }
        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }
        private byte read()
        {
            if (isEof) return 0;
            if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } }
            return buf[ptr++];
        }
        public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; }

        public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n'; b = (char)read())
                if (b == 0) break;
                else if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long()
        {
            if (isEof) return long.MinValue;
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != 0 && b != '-' && (b < '0' || '9' < b));
            if (b == 0) return long.MinValue;
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
        public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; }
        private T[] enumerate<T>(int n, Func<T> f)
        {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f();
            return a;
        }

        public char[] Char(int n) { return enumerate(n, Char); }
        public string[] Scan(int n) { return enumerate(n, Scan); }
        public double[] Double(int n) { return enumerate(n, Double); }
        public int[] Integer(int n) { return enumerate(n, Integer); }
        public long[] Long(int n) { return enumerate(n, Long); }
    }
}
#endregion