package main

import (
    "fmt"
)

func main() {
    var w, h, n int64
    fmt.Scan(&w, &h, &n)
    ms := make(map[int64]bool)
    mk := make(map[int64]bool)
    for i := int64(0); i < n; i++ {
        var s, k int64
        fmt.Scan(&s, &k)
        ms[s] = true
        mk[k] = true
    }
    sum := int64(0)
    sum = int64(len(ms)) * h + int64(len(mk)) * w -
            int64(len(mk)) * int64(len(ms)) - n
    fmt.Println(sum)
}