Problem:
Score : 300 points

Problem Statement

Given is a sequence of integers A_1, A_2, ..., A_N.
If its elements are pairwise distinct, print YES; otherwise, print NO.

Constraints

2 ≤ N ≤ 200000

1 ≤ A_i ≤ 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 ... A_N

Output

If the elements of the sequence are pairwise distinct, print YES; otherwise, print NO.

Sample Input 1

5
2 6 1 4 5

Sample Output 1

YES

The elements are pairwise distinct.

Sample Input 2

6
4 1 3 1 6 2

Sample Output 2

NO

The second and fourth elements are identical.

Sample Input 3

2
10000000 10000000

Sample Output 3

NO

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

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

namespace AtCoder
{
	class Program
	{
		public static void Main()
		{
#if TextInput
			using(var reader = new StreamReader(Debug.SampleTextPath)) 
			{
				Console.SetIn(reader);
#endif
				var num = IO.ReadInt();
				IO.Write(IO.ReadIntArray().Distinct().Count() == num);
				
#if TextInput
			}
#endif
		}

		
	}

	public static class IO
	{
		public static string   Read()								 { return Console.ReadLine(); }
		public static string[] ReadArray(char iSplitter = ' ')		 { return Read().Split(iSplitter); }
		public static int	   ReadInt()							 { return int.Parse(Read()); }
		public static int[]	   ReadIntArray(char iSplitter = ' ')	 { return ReadArray().Select(iText => int.Parse(iText)).ToArray(); }
		public static long	   ReadLong()							 { return int.Parse(Read()); }
		public static long[]   ReadLongArray(char iSplitter = ' ')	 { return ReadArray().Select(iText => long.Parse(iText)).ToArray(); }
		public static double   ReadDouble()							 { return double.Parse(Read()); }
		public static double[] ReadDoubleArray(char iSplitter = ' ') { return ReadArray().Select(iText => double.Parse(iText)).ToArray(); }
		public static char[]   ReadCharArray()						 { return Read().ToCharArray(); }

		public static void Write(string iValue)	 { Console.WriteLine(iValue); }
		public static void Write(int iValue)	 { Console.WriteLine(iValue); }
		public static void Write(long iValue)	 { Console.WriteLine(iValue); }
		public static void Write(double iValue)  { Console.WriteLine(iValue); }
		public static void Write(decimal iValue) { Console.WriteLine(iValue); }
		public static void Write(bool iValue)	 { Console.WriteLine(iValue ? "Yes" : "No"); }
		public static void Write<Type>(IEnumerable<Type> iValue , string iJoinWord = " ") { Console.WriteLine(string.Join(iJoinWord , iValue)); }
	}

	public static class Util
	{
		public static long Gcd(long i0 , long i1) { return (i0 > i1) ? _Gcd(i0 , i1) : _Gcd(i1 , i0); }
		public static long Lcm(long i0 , long i1) { return (i0 * i1) / Gcd(i0 , i1); }
		public static long ModPow(long iBaseNumber , long iPow , long iModNumber)
		{
			var num = 1L;
			while(iPow != 0)
			{
				if((iPow & 0x1) != 0)
				{
					num = (num * iBaseNumber) % iModNumber;
				}
				iBaseNumber = (iBaseNumber * iBaseNumber) % iModNumber;
				iPow >>= 1;
			}
			return num;
		}
		public static long CombinationNum(int iLeftNumber , int iRightNumber)
		{
			if(iRightNumber == 0) { return 1; }
			if(iLeftNumber == 0)  { return 0; }
			return iLeftNumber * CombinationNum(iLeftNumber - 1 , iRightNumber - 1) / iRightNumber;
		}

		private static long _Gcd(long i0 , long i1)	{ return (i1 == 0) ? i0 : _Gcd(i1 , i0 % i1); }
	}

	public class UnionFind
	{
		public int[] Parents;
		public int[] RootNums;
		public UnionFind(int iRootNum)
		{
			Parents = Enumerable.Range(0 , iRootNum).ToArray();
			RootNums = new int[iRootNum];
		}
		public void Normalize()
		{
			for(var iIndex = 0 ; iIndex < Parents.Length ; ++ iIndex)
			{
				var rootIndex = _GetRoot(iIndex);
				++ RootNums[rootIndex];
				Parents[iIndex] = rootIndex;
			}
		}
		public void Union(int iNumber0 , int iNumber1)
		{
			var rootNumber0 = _GetRoot(iNumber0);
			var rootNumber1 = _GetRoot(iNumber1);
			if(rootNumber0 < rootNumber1)
			{
				Parents[rootNumber1] = rootNumber0;
			}
			else
			{
				Parents[rootNumber0] = rootNumber1;
			}
		}
		public int _GetRoot(int iNumber)
		{
			return (Parents[iNumber] == iNumber) ? iNumber : _GetRoot(Parents[iNumber]);
		}
	}
}