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>
#include<iomanip>
using namespace std;
typedef long long ll;
typedef long  l;
typedef pair<int,int> P;
#define rep(i,n) for(int i=0;i<n;i++)
#define fs first
#define sc second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define ALL(A) A.begin(),A.end()
const double PI=3.141592653589;
const int INF=1000000007;
const ll LMAX=1000000000000001;
const ll mod=1000000007;
ll gcd(ll a,ll b){if(a<b)swap(a,b);while((a%b)!=0){a=b;b=a%b;}return b;}
int dx[]={-1,0,1,0};
int dy[]={0,1,0,-1};


int main(){
  set<int> s;
  int n; cin>>n;
  bool f=0;
  rep(i,n){
    int a; cin>>a;
    if(s.count(a)) f=1;
    else s.insert(a);
  }
  if(f)
  puts("NO");
  else
  puts("YES");


  return 0;
}