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)

/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author champon
 */

#include <iostream>
#include <fstream>

#include <bits/stdc++.h>
#define ok cout << "ok" << endl;
#define sp << " " <<
using namespace std;
typedef long long ll;
const ll mod = 1e9+7;
const ll inf = 9e18;
template<typename T1, typename T2> ll ceill(T1 a, T2 b){ return (a+b-1)/b; }
void ans(bool b, ostream& out=cout){ out << (b ? "Yes" : "No") << endl; }
void ans2(bool b, ostream& out=cout){ out << (b ? "YES" : "NO") << endl; }
template<typename T> inline bool chmax(T &a, T b){ if(a<b){a=b; return true;} return false; }
template<typename T> inline bool chmin(T &a, T b){ if(a>b){a=b; return true;} return false; }
template<typename A, size_t N, typename T> void Fill(A (&array)[N], const T &val){fill((T*)array, (T*)(array+N), val);}
int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
int dy[] = {0, 1, 0, -1, 1, -1, -1, 1};

#ifndef INCLUDE_DEBUG_HPP
#define INCLUDE_DEBUG_HPP

#include <iostream>
#include <vector>
#include <map>
using namespace std;

class debug
{
public:
    typedef long long ll;
    template<typename T> void vd(vector<T> vec);
    template<typename T> void vd2(vector<vector<T>> vec);
    template<typename T> void vpd(vector<pair<int, int>> vec);
    template<typename T> void ad(T *arr, ll n);
    template<typename T, size_t N> void ad2(T (&arr)[N], ll n);
    template<typename T> void md(T mp);
};

#endif //INCLUDE_DEBUG_HPP

template<typename T> void debug::vd(vector<T> vec)
{
    for(auto vv : vec) cout << vv << " ";
    cout << endl;
}

template<typename T> void debug::vd2(vector<vector<T>> vec)
{
    for(auto vv : vec) for(auto vvv : vv) cout << vvv << " ";
    cout << endl;
}

template<typename T> void debug::vpd(vector<pair<int, int>> vec) {
    for(auto const& vv : vec) {
        cout << vv.first << " " << vv.second << endl;
    }
    cout << endl;
}

template<typename T> void debug::ad(T *arr, ll n)
{
    for(int i=0; i<=n; i++) cout << arr[i] << " ";
    cout << endl;
}

template<typename T, size_t N> void debug::ad2(T (&arr)[N], ll n)
{
    for(int i=0; i<=N; i++) for(int j=0; j<=n; j++) cout << arr[i][j] << " ";
    cout << endl;
}

template<typename T> void debug::md(T mp)
{
    cout << "key : value" << endl;
    for(auto const& m : mp) cout << m.first << " : " << m.second << endl;
    cout << endl;
}
debug debug;

class CDistinctOrNot {
public:
	void solve(std::istream& in, std::ostream& out)
	{
	    int n;
	    in >> n;
	    vector<ll> a(n);
	    for(int i=0; i<n; i++){
	        in >> a[i];
	    }

	    set<ll> s;
	    for(int i=0; i<n; i++){
	        s.insert(a[i]);
	    }

	    ans2(s.size() == n, out);
	}
};


int main() {
	CDistinctOrNot solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
	return 0;
}