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;
typedef long long int lli;
const int INF = 1e9 + 100;
const lli INF64 = (1LL << 61) + 100;
const lli MOD = 1000*1000*1000+7;
lli bpow(lli a, lli b) {
	if(b == 0) return 1;
	if(b == 1) return a % MOD;
	lli r = bpow(a, b >> 1);
	r = (r * r) % MOD;
	return (r * (((b&1)?a:1) % MOD)) % MOD;
}
lli multInverse(lli a) {
	return bpow(a, MOD - 2);
}
lli modMult(lli a, lli b) {
	return (a * b) % MOD;
}
lli modSub(lli a, lli b) {
	a += MOD;
	lli r = a - b;
	if(r >= MOD) return r - MOD;
	return r;
}
lli modAdd(lli a, lli b) {
	lli r = a + b;
	if(r >= MOD) return r - MOD;
	return r;
}
signed main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	//	freopen("input.txt", "r", stdin);
	//	freopen("output.txt", "w", stdout);
	int n;
	cin >> n;
	set<int> aa;
	for(int i = 1; i <= n; i++) {
		int inp;
		cin >> inp;
		aa.insert(inp);
	}
	cout << (aa.size() == n ? "YES" : "NO") << "\n";
	return 0;
}