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 ed cout << "\n";
#define speed                         \
    ios_base::sync_with_stdio(false); \
    cin.tie(NULL);                    \
    cout.tie(NULL);
#define ll long long
#define ffor(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(i, n) ffor(i, 0, n)
#define All(obj) (obj).begin(), (obj).end()
#define INF ((ll)1e9 + 7)
#define c(a) cout << a << "\n";
using namespace std;
const int N = 100005;

int main()
{
    speed;
    cout << fixed << setprecision(6);
    /*start*/
    int n;
    cin >> n;
    set<ll> s;
    rep(i, n)
    {
        ll b;
        cin >> b;
        s.insert(b);
    }
    if (s.size() == n)
    {
        c("YES");
    }
    else
    {
        c("NO");
    }
    return 0;
}