How many inversions?

Count the number of inversions of every given sequence of $n$ integer numbers $x_1 \dots x_n$ . Remember that an inversion is a pair of indices $i$ and $j$ such that $1 \le i < j \le n$ and $x_i > x_j$ .

Input

Input consists of several cases, each one with $n$ followed by the $n$ integer numbers $x_1 \dots x_n$ . Assume $0 \le n \le 50000$ .

Output

For every case, print the number of inversions of the sequence.

Problem information

Author: Salvador Roura

Generation: 2026-01-25T11:50:34.216Z