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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define mod 1000000007
#define pb push_back
#define pii pair<ll,ll>
#define pi pair<int ,int> 
#define REP(i,a,n) for(int i=a;i<n;i++)
#define rep(i,a,n) for(int i=a;i>=n;i--)
#define F first
#define S second
int main()
{    
    
   int n;
   cin>>n;
   map<int,int>mp;int check=0;
   REP(i,0,n)
   {
       int x;
       cin>>x;
       
       if(mp.find(x)==mp.end()){mp[x]++;}
       else{check=1;}
   }
   if(check==0)
   {
       cout<<"YES";
   }
   else
   {
       cout<<"NO";
   }
    return 0;
}