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;
void Main();

using i8  = int8_t;   /* -128 ~ 127 */
using u8  = uint8_t;  /* 0 ~ 255 */
using i16 = int16_t;  /* -32,768 ~ 32,767 */
using u16 = uint16_t; /* 0 ~ 65,535 */
using i32 = int32_t;  /* -2,147,483,648 ~ 2,147,483,647 */
using u32 = uint32_t; /* 0 ~ 4,294,967,295 */
using i64 = int64_t;  /* -9,223,372,036,854,775,808 ~ 9,223,372,036,854,775,807 */
using u64 = uint64_t; /* 0 ~ 18,446,744,073,709,551,615 */
using f32 = float;    /* (-3.4 * 10^38) ~ (3.4 * 10^38) */
using f64 = double;   /* (-1.7 * 10^308) ~ (1.7 * 10^308) */
using f80 = __float80;
template <class T> using Vec = vector<T>;
constexpr i64 INF = 1010000000000000017;
constexpr i64 MOD = 1e9 + 7;
constexpr f64 EPS = 1e-12;
constexpr f64 PI = 3.14159265358979323846;
#define ALL(v) v.begin(), v.end()
#define GCD(a, b) __gcd(a, b) /* 最大公約数 */
#define LCM(a, b) a / __gcd(a, b) * b /* 最小公倍数 */

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
    Main();
    return 0;
}

void Main() {
    u32 N;
    cin >> N;
    Vec<u64> A(N);
    for (u32 i = 0; i < N; i++) cin >> A[i];
    sort(ALL(A));
    string res = "YES";
    for (u32 i = 1; i < N; i++) {
        if (A[i - 1] == A[i]) res = "NO";
    }
    cout << res << endl;
}