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: Wrong Answer)

#include<bits/stdc++.h>
typedef long long int   LL;
typedef long double     LD;
#define OR              ||
#define AND             &&
#define nl              '\n'
#define S               string
#define inf             INT_MAX
#define SQR(a)          (a) * (a)
#define GCD(a, b)       __gcd(a, b)
#define pi              2.0*acos(0.0)
#define LCM(a, b)       (a * b) / GCD(a, b)
#define mem(a,b)        memset(a,b,sizeof(a))
#define srtv(v)         sort(v.begin(),v.end())
#define T               int t; cin>>t; while(t--)
#define boost		    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
#define inout           freopen("input.txt","r",stdin);freopen("output.txt","w",stdout)
using namespace std;


int main()
{
    LL n;
    cin>>n;

    LL a[n+1];

    for(int i=0;i<n;i++)
    {
        cin>>a[i];
    }

    if(n==2)
    {
        if(a[0]!=a[1])
        {
            cout<<"YES";
        }
        else
            cout<<"NO";
    }

    else
    {
    int flag=0;

    for(int i=1;i<n-1;i++)
    {
        if(a[i]+a[i-1]==a[i]+a[i+1])
        {
            flag=1;
            break;
        }
    }

    if(flag==0)
        cout<<"YES";
    else
        cout<<"NO";
    }

    return 0;
}

/*

*/