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>
#define ll long long int
#define ul unsigned long long int
#include<vector>
#define mp make_pair
#define endl "\n"
#define fio ios_base::sync_with_stdio(false);cin.tie(NULL);
#define lb lower_bound
#define forn(i,n) for(ll i=0 ; i<n ; i++)
#define arr(a,n) for(ll i=0;i<n;i++){ cin>>a[i]; }
#define ub upper_bound
#define pb push_back
#define mod 1000000007
using namespace std;

ll ipow(ll x, ll n) 
{ 
    ll result = 1; 
    while (n) { 
        if (n & 1) 
            result = result * x % mod; 
        n = n / 2; 
        x = x * x % mod; 
    } 
    return result; 
} 

int main(){
	fio
	unordered_map<int,int>m;
	int n;
	cin>>n;
	int a[n];
	int flag=0;
	for(int i=0;i<n;i++)
	{
		cin>>a[i];
	m[a[i]]++;
	}
	for(auto x : m){
		if(x.second>1){
			
			flag=1;
			break;
		}
	}
	if(flag==1){
		cout<<"NO"<<endl;
	}
	else
	cout<<"YES"<<endl;
	
return 0;
}