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 Fortran (gfortran v4.8.4) (judge verdict: Wrong Answer)

program main
	implicit none
    integer i,j,n,flag,l,k,tmp
    integer,allocatable :: a(:)
    
    flag=1 !distinct
    
    read(*,*) n
    allocate(a(n))
    read(*,*) (a(i),i=1,n)
    
    l=n/2+1
    k=n
    do while(k/=1)
      if(l<1)then
        l=l-1
        tmp=a(l)
      else
        tmp=a(k)
        a(k)=a(1)
        k=k-1
        if(k==1) then
           a(1)=tmp
           exit
        endif
     endif
     i=l
     j=l+l
     do while(j<=k)
        if(j<k)then
           if(a(j).lt.a(j+1))j=j+1
        endif
        if (tmp<a(j))then
           a(i)=a(j)
           i=j
           j=j+j
        else
           j=k+1
        endif
     enddo
     a(i)=tmp
  enddo
  do i=1,n
     if (a(i)==a(j)) then
        flag=0
        goto 99
     end if
  end do
99 continue
    if (flag==1) then
       write(*,'(a)') 'YES'
    else
       write(*,'(a)') 'NO'
    end if
end program main