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;
#define int long long
#define IOS ios_base::sync_with_stdio(false);cin.tie(NULL);
#define pb push_back 
#define eb emplace_back
#define fn for(int i =0 ;i <n;i++)
#define fn1 for( int i =1;i<=n;i++)
#define fm for(int j =0 ;j <m;j++)
#define fm1 for(int j =1;j<=m;j++)
#define fi first
#define se second
#define E endl
#define MOD 1000000007
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
const int N = 2e6+5;
const int INF = 1e18L;
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
  cerr << name << ": " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
  const char* comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << ": " << arg1 << " |";
  __f(comma + 1, args...);
}
int ar[N];
int dp[N];
signed main(){
	// #ifndef ONLINE_JUDGE
	// freopen("input.txt","r",stdin);
	// freopen("output.txt","w",stdout);
	// #endif
	IOS;
	int T=1;
	// cin >> T;
	while(T--){
		int n;
		cin >> n ;
		map<int,int>mp;
		fn{
			int x;
			cin>>x;
			mp[x]++;
			if(mp[x]==2){
				return cout <<"NO",0;
			}
		}
		cout<<"YES";
	
	}
	cerr << "Time Taken : " << 1.0 * clock() / CLOCKS_PER_SEC << " sec \n";
	return 0;
}