// http://yukicoder.me/problems/30

open System

let dprintfn fmt = Printf.kprintf Diagnostics.Debug.WriteLine fmt

[<EntryPoint>]
let main argv = 
    let W = Console.ReadLine().Trim() |> int
    let H = Console.ReadLine().Trim() |> int
    let N = Console.ReadLine().Trim() |> int
    let suits = Array.create (W) false
    let nums = Array.create (H) false
    let w = ref 0
    let h = ref 0
    for i=1 to N do
        let S, K = Console.ReadLine().Trim().Split([|' '|]) |> Array.map int |> fun a -> a.[0]-1, a.[1]-1
        if suits.[S] = false then
            incr w
            suits.[S] <- true
        if nums.[K] = false then 
            incr h
            nums.[S] <- true
    let W = int64 W
    let H = int64 H
    let w = int64 !w
    let h = int64 !h
    let ans = W*H - (W - w)*(H - h) - int64 N
    printfn "%d" ans
    0