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 ll long long
#define pb push_back
#define mem(dp, v) memset(dp, v, sizeof dp)
using namespace std;
const ll N = 1e5 + 7, inf = 1e17;
ll ar[N], br[N];
//string s;
//ll foo(int i, int j)
//{//cout<<"dsa";
//    ll &ret = dp[i][j];
//    if(i == j) return 1;
//    if(i > j) return 0;
//    if(ret != -1) return ret;
//    ll ans = 0;
//    if(s[i] == s[j]) ans = (1 + foo(i + 1, j - 1)) + foo(i + 1, j) + foo(i, j - 1)- foo(i + 1, j - 1);
//    else ans = foo(i + 1, j) + foo(i, j - 1) - foo(i + 1, j - 1);
//    return ret = ans;
//}
int main()
{
    map<ll, ll>mp;
    string s;
    ll n, m, k, okay = 1;;
    cin>>n;
    for(int i = 0; i < n; i++)
    {
        ll x;
        cin>>x;
        if(mp[x])
        {
            okay = 0;
        }
        mp[x] = 1;
    }
    if(okay) puts("YES");
    else puts("NO");
    return 0;
}