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 <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <cmath>
#include <map>

#define int long long
#define double long double
#define incin(n) int (n); cin >> (n)
using namespace std;
namespace math
{
	double PI = 3.14159265359;
	int step(int n);
	int ncr(int n,int r);
	int npr(int n,int r);
	int gcm(int a,int b);

	int step(int n){
		if(n<=1){
			return 1;
		}else{
			return n * step(n-1);
		}
	}
	int ncr(int n,int r){
		for(int i=1;i<r;i++){
			n *= n-i;
		}
		for(int i=1;i<r;i++){
			r *= r-1;
		}
		return n/r;
	}
	int npr(int n,int r){
		for (int i = 1; i < r; ++i)
		{
			n *= n-1;
		}
		return n;
	}
	int gcm(int a,int b){
		int p=max(a,b);
		int q=min(a,b);
		int r;
		while(true){
			if(p%q==0){
				return q;
			}
			r = p%q;
			p=q;
			q=r;
		}
	}
}


using namespace std;

signed main (){
	int n;
	cin >> n;
	vector<int> a(n);
	for(int i = 0;i<n;i++){
		cin >> a.at(i);
	}
	int size = a.size();
	sort(a.begin(),a.end());
	a.erase(unique(a.begin(),a.end()),a.end());
	if(a.size()==size){
		cout<<"YES"<<endl;
	}else{
		cout<<"NO"<<endl;
	}
	return 0;
}