func solve(m : Int, n: Int) -> Int {
    if n == 1 && m == 1 {
        return 0
    }
    let a = min(m, n)
    let b = max(m, n)
    let c = b / 2
    
    return 1 + 2 * solve(min(a, c), n: max(a, c)) + (b % 2) * a;
}

let param = readLine()!.characters.split(" ").map { Int(String($0))! }
print(solve(param[0], n: param[1]))