import * as fs from "fs"

type Input = (args: string) => void

function add(a: bigint, b: number): bigint {
    return a + BigInt(b)
}

const main: Input = args => {
    const input = args.trim().split("\n");
    const [n, h, w] = input.shift().split(" ").map(x => BigInt(x))
    let ans = (add(h + w, -2)) * (add(n, 1) / BigInt(2) * (n / BigInt(2)))
    console.log(String(ans))
}

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