Problem:
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The Number of Inversions

For a given sequence $A = \{a_0, a_1, ... a_{n-1}\}$, the number of pairs $(i, j)$ where $a_i > a_j$ and $i < j$, is called the number of inversions. The number of inversions is equal to the number of swaps of Bubble Sort defined in the following program:

bubbleSort(A)
cnt = 0 // the number of inversions
for i = 0 to A.length-1
for j = A.length-1 downto i+1
if A[j] < A[j-1]
swap(A[j], A[j-1])
cnt++

return cnt

For the given sequence $A$, print the number of inversions of $A$. Note that you should not use the above program, which brings Time Limit Exceeded.

Input

In the first line, an integer $n$, the number of elements in $A$, is given. In the second line, the elements $a_i$ ($i = 0, 1, .. n-1$) are given separated by space characters.

output

Print the number of inversions in a line.

Constraints

$ 1 \leq n \leq 200,000$

$ 0 \leq a_i \leq 10^9$

$a_i$ are all different

Sample Input 1

5
3 5 2 1 4

Sample Output 1

6

Sample Input 2

3
3 1 2

Sample Output 2

2

Solution in Ruby (judge verdict: Wrong Answer)

def bsort(a,n)
  cnt=0
  n.times do |i|
    if a[i]>a[i+1] then
      a[i],a[i+1]=a[i+1],a[i]
      cnt+=1
    end
  end
  if n>1 then
    cnt+=bsort(a,n-1)
  end
  return cnt
end

n=gets.to_i
a=gets.split.map!{|i|i.to_i}
a.slice!(n..-1)
cnt=bsort(a,n-1)
n.times do |i|
  print a[i]," "
end
print "\n",cnt