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 (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
int quicksort (int a[],int low,int high);
int main()
{
    int n;
    int a[200010];
    int m,b,flag=0;
    scanf("%d",&n);
    for(int i=0;i<n;i++)
        scanf("%d",&a[i]);
    quicksort(a,0,n-1);
    for(int i=0;i<n-1;i++)
        if(a[i]==a[i+1]) {flag=1;break;}
    if(flag==1) printf("NO");
    else printf("YES");
    return 0;
}
int quicksort (int a[],int low,int high)
{
    int temp,t;
    int i,j;
    if(low>high)
        return ;
    temp=a[low];
    i=low;j=high;
    while(i!=j)
    {
        while(a[j]>=temp && j>i) j--;
        while(a[i]<=temp && i<j) i++;
        if(i<j)
            {t=a[i];a[i]=a[j];a[j]=t;}
    }
    a[low]=a[i];
    a[i]=temp;
    quicksort(a,low,i-1);
    quicksort(a,i+1,high);
    return ;

}