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: Runtime Error)

#include <bits/stdc++.h>
using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
template<class T> inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template<class T> inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
int64_t abs(int64_t n) {
  if (n < 0) {
    n = -n;
  }
  return n;
}

int main() {
  int n;
  cin >> n;
  vector <int64_t> v(n);
  int64_t max = 0;
  rep(i, n) {
    cin >> v.at(i);
    if (v.at(i) > max) {
      max = v.at(i);
    }
  }
  vector <int> data(max, 0);
  int tmp = 0;
  rep(i, n) {
    if (data.at(v.at(i)-1) == 1) {
      cout << "NO" << endl;
      tmp++;
      break;
    } else {
      data.at(v.at(i)-1)++;
    }
  }
  if (tmp == 0) {
    cout <<  "YES" << endl;
  }
}