Problem:
Problem A: Hanafuda Shuffle

There are a number of ways to shuffle a deck of cards. Hanafuda
shuffling for Japanese card game 'Hanafuda' is one such example.
The following is how to perform Hanafuda shuffling.

There is a deck of n cards. Starting from the p-th card
from the top of the deck, c cards are pulled out
and put on the top of the deck, as shown in Figure 1.
This operation, called a cutting operation, is repeated.

Write a program that simulates Hanafuda shuffling and answers which
card will be finally placed on the top of the deck.

Figure 1: Cutting operation

Input

The input consists of multiple data sets.
Each data set starts with a line containing two positive integers n
(1 <= n <= 50) and r (1 <= r <= 50); n and
r are the number of cards in the deck and the number of cutting
operations, respectively.

There are r more lines in the data set, each of which
represents a cutting operation. These cutting operations
are performed in the listed order.
Each line contains two positive integers p and c
(p + c <= n + 1).
Starting from the p-th card from the top of the deck, c
cards should be pulled out and put on the top.

The end of the input is indicated by a line which contains two zeros.

Each input line contains exactly two integers separated by a space
character.
There are no other characters in the line.

Output

For each data set in the input, your program
should write the number of the top card after the shuffle.
Assume that at the beginning the cards
are numbered from 1 to n, from the bottom to the top.
Each number should be written in a separate line
without any superfluous characters such as leading or following spaces.

Sample Input

5 2
3 1
3 1
10 3
1 10
10 1
8 3
0 0

Output for the Sample Input

4
4

Solution in C# (judge verdict: Accepted)

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

namespace ProgrammingContest
{
    class MainClass : IDisposable
    {
        Scanner sc;
        Writer wr;

        public MainClass()
        {
            

            this.wr = new Writer(this.isReactive);
            //this.wr = new Writer(this.outFilePath);
#if DEBUG
            if (!this.isReactive)
            {
                this.sc = new Scanner(this.inFilePath);
            }
            else
            {
                this.sc = new Scanner();
            }
#else
            this.sc = new Scanner();
#endif
        }
        static void Main(string[] args)
        {
            using (var mainClass = new MainClass())
            {
                //mainClass.MakeTestCase();
                mainClass.Solve();
            }
        }

        public void Dispose()
        {
            if (this.sc != null)
            {
                this.sc.Dispose();
                this.sc = null;
            }
            if (this.wr != null)
            {
                this.wr.Dispose();
                this.wr = null;
            }
        }

        void MakeTestCase()
        {
            //Random rand = new Random();
            //this.wr = new Writer(inFilePath);


        }

        void Solve()
        {
            for (int n = sc.NextInt, r = sc.NextInt; n != 0 && r != 0; n = sc.NextInt, r = sc.NextInt)
            {
                int[] card = Enumerable.Range(1, n).Reverse().ToArray();
                for (int i = 0; i < r; i++)
                {
                    int p = sc.NextInt - 1;
                    int c = sc.NextInt;
                    int[] tmp = new int[c];
                    for (int j = 0; j < c; j++)
                    {
                        tmp[j] = card[p + j];
                    }
                    for (int j = p - 1; j >= 0; j--)
                    {
                        card[j + c] = card[j];
                    }
                    for (int j = 0; j < c; j++)
                    {
                        card[j] = tmp[j];
                    }
                }
                wr.WriteLine(card.First());
            }
        }

        bool isReactive = false; // TODO: reactive check !!
    }

    class Writer : IDisposable
    {
        private System.IO.TextWriter writer;
        private StringBuilder sb;
        private bool isReactive;
        public Writer(string path) : this(new System.IO.StreamWriter(path))
        {
        }
        public Writer(bool isReactive) : this(null, isReactive)
        {
        }
        public Writer(System.IO.TextWriter writer = null, bool isReactive = false)
        {
            this.writer = (writer ?? Console.Out);
            this.isReactive = isReactive;
            if (!this.isReactive)
            {
                this.sb = new StringBuilder();
            }
        }
        public void Dispose()
        {
            if (!this.isReactive)
            {
                this.writer.Write(sb.ToString());
            }
            if (!this.writer.Equals(Console.Out))
            {
                this.writer.Dispose();
            }
        }
        public void Write(object val)
        {
            if (this.isReactive)
            {
                this.writer.Write(val.ToString());
                this.writer.Flush();
            }
            else
            {
                this.sb.Append(val.ToString());
            }
        }
        public void Write(string format, params object[] vals)
        {
            if (this.isReactive)
            {
                this.writer.Write(format, vals);
                this.writer.Flush();
            }
            else
            {
                this.sb.AppendFormat(format, vals);
            }
        }
        public void WriteLine(object val = null)
        {
            this.Write((val ?? string.Empty).ToString() + System.Environment.NewLine);
        }
        public void WriteLine(int val)
        {
            this.WriteLine(val.ToString());
        }
        public void WriteLine(long val)
        {
            this.WriteLine(val.ToString());
        }
        public void WriteLine(string val)
        {
            this.WriteLine((object)val);
        }
        public void WriteLine(string format, params object[] vals)
        {
            this.Write(format + System.Environment.NewLine, vals);
        }
    }

    class Scanner : IDisposable
    {
        private Queue<string> buffer;
        private char[] sep;
        private System.IO.TextReader reader;
        public Scanner(string path, char[] sep = null) : this(new System.IO.StreamReader(path), sep)
        {
        }
        public Scanner(System.IO.TextReader reader = null, char[] sep = null)
        {
            this.buffer = new Queue<string>();
            this.sep = (sep ?? new char[] { ' ' });
            this.reader = (reader ?? Console.In);
        }
        private void CheckBuffer()
        {
            if (this.buffer.Count == 0)
            {
                string str = string.Empty;
                for (; string.IsNullOrEmpty(str);
                    str = this.reader.ReadLine()) ;

                str.Split(this.sep).ToList()
                   .ForEach(el => this.buffer.Enqueue(el));
            }
        }

        public void Dispose()
        {
            if (!this.reader.Equals(Console.In))
            {
                this.reader.Dispose();
            }
        }

        public string Next
        {
            get
            {
                this.CheckBuffer();
                return this.buffer.Dequeue();
            }
        }
        public string[] GetStringArray(int N)
        {
            return Enumerable.Range(0, N)
                             .Select(e => this.Next)
                             .ToArray();
        }

        public int NextInt
        {
            get
            {
                return int.Parse(this.Next);
            }
        }
        public int[] GetIntArray(int N)
        {
            return Enumerable.Range(0, N)
                             .Select(e => this.NextInt)
                             .ToArray();
        }

        public double NextDouble
        {
            get
            {
                return double.Parse(this.Next);
            }
        }
        public double[] GetdoubleArray(int N)
        {
            return Enumerable.Range(0, N)
                             .Select(e => this.NextDouble)
                             .ToArray();
        }

        public long NextLong
        {
            get
            {
                return long.Parse(this.Next);
            }
        }
        public long[] GetLongArray(int N)
        {
            return Enumerable.Range(0, N)
                             .Select(e => this.NextLong)
                             .ToArray();
        }

        public bool IsEnd
        {
            get
            {
                this.CheckBuffer();
                return this.buffer.Count == 0;
            }
        }
    }
}