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 rep(i,n) for(int i=0 ; i<(n) ; i++)
#define repr(i,n) for(int i=(n) ; i>=0 ; i--)
#define ALL(x) (x).begin(),(x).end()

typedef long long ll;
typedef unsigned long long ull;
 
const ll INF = 1LL<<60;
const int MINF = 1e9;
const int MOD = 1e9+7;

using vi = vector<int>;
using vii = vector<vi>;

template<typename T> bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<typename T> bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

template<typename T>
T GCD(T a,T b){ return b ? GCD(b,a%b) : a ;}
template<typename T>
T LCM(T a,T b){ return a*b / GCD(a,b) ;}

int main(){
    int n;cin >> n;
    vi a(n);
    rep(i,n)cin >> a[i];

    int a_size = a.size();
    sort(ALL(a));
    a.erase(unique(ALL(a)), a.end());
    if(a_size == a.size())cout << "YES" << endl;
    else cout << "NO" << endl;
    return 0;
}