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ans.cs

using System;
using System.Linq;

namespace PlayGrournd
{
	class MainClass
	{
		public static void Main(){
			var line = System.Console.ReadLine().Trim();
			string[] words = line.Split(' ');
			var sheetCount = System.Convert.ToInt32(words[0]);
			var length = System.Convert.ToInt32(words[1]);
			System.Collections.Generic.List<bool> sheets = new System.Collections.Generic.List<bool>( new bool[sheetCount] ){};
			for(int i = 0; i < length; i++ ){
				var input2 = System.Console.ReadLine();
				var w = input2.Split(' ');
				var count = System.Convert.ToInt32(w[0]);
				var sheet = System.Convert.ToInt32(w[1]);
				//test
				bool test = true;
				for(int x = 0; x < count; x++ ){
					var target = sheet + x -1;
					target = target >= sheets.Count ? ( target - sheets.Count ) : target ;
					if (sheets [target] == false) {
						continue;
					} else {
						test = false;
						break;
					}
				}
				if (test == false)
					continue;

				//do
				for(int x = 0; x < count; x++ ){
					var target = sheet + x -1;
					target = target >= sheets.Count ? ( target - sheets.Count ) : target ;
					sheets [target] = true;

				}

				// current
				//sheets.ForEach( a => System.Console.WriteLine( a ) );
			}
			//System.Console.WriteLine("");
			var c = sheets.Where( d => d == true ).Count();
			System.Console.WriteLine( c );
		}
	}
}