import * as fs from "fs"

class BinaryIndexedTree {
    data: number[]
    size: number
    constructor(size: number) {
        this.size = size
        this.data = Array(size).fill(0)
    }
    public add(p: number, x: number): void {
        p++;
        while (p <= this.size) {
            this.data[p - 1] += x;
            p += p & -p
        }
    }

    public range_sum(l: number, r: number): number {
        return this.sum(r) - this.sum(l)
    }

    private sum(p: number): number {
        let res = 0
        while (p > 0) {
            res += this.data[p - 1]
            p -= p & -p
        }
        return res
    }
}

type Input = (args: string) => void

const main: Input = args => {
    const input = args.trim().split("\n");
    const n = +input.shift()
    const p = input.shift().split(" ").map(x => +x)
    const bit = new BinaryIndexedTree(n + 1);

    let ans = 0
    p.forEach(x => {
        ans += bit.range_sum(x + 1, n + 1)
        bit.add(x, 1)
    })
    console.log(ans)
}

main(fs.readFileSync('/dev/stdin', 'utf8'));