use ac_library::FenwickTree;
use itertools::Itertools;
use proconio::input;

fn main() {
    input! {
        n: usize,
        a: [usize; n],
    }

    let mut bit = FenwickTree::new(n, 0);
    let mut ans = 0usize;
    for i in (0..n).sorted_unstable_by_key(|&i| a[i]) {
        ans += bit.sum(i..);
        bit.add(i, 1);
    }
    println!("{ans}");
}