//Enter your code here. Read input from STDIN. Print output to STDOUTmodule console

open System
open System.IO

let rec folds n m = if n = 1 then m - 1
                    else if m = 1 then n - 1
                    else 1 + (folds 1 m) + (folds (n - 1) m)


[<EntryPoint>]
let main argv =
    let s = Console.ReadLine()
    match s.Split() |> Array.map int with
        | [|n;  m|] -> folds n m |> printfn "%d"
        | _ -> failwith "Invalid input"
    0 // return an integer exit code