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 REP(i, n) for (ll i = 0; i < (n); i++)
#define FOR(i, m, n) for(ll i = m;i < n;i++)
#define VSORT(v) sort(v.begin(), v.end());
using namespace std;
using ll = long long;
using vll = vector<ll>;

int gcd(int a, int b) {
    if (b==0) return a;
   	else return gcd(b, a%b);
}
int lcm(int a, int b) {
    return a * b / gcd(a, b);
}

int main(){
	ll N;
	cin>>N;
	vll A(N);
	REP(i,N)cin>>A[i];
	VSORT(A);
	
	int T=0;
	REP(i,N-1){
		if(A[i]!=A[i+1]) T++;
	}
	
	if(T==N-1)cout<<"YES"<<endl;
	else cout<<"NO"<<endl;
	
}