let i = require('fs').readFileSync('/dev/stdin', 'utf8').split('\n')
let w = parseInt(i[0])
let h = parseInt(i[1])
let n = parseInt(i[2])
let wl = []
let hl = []
for (let c = 3; c < i.length - 1; c++) {
  let sk = i[c].split(' ').map((e) => parseInt(e))
  if (wl.indexOf(sk[0]) == -1) wl.push(sk[0])
  if (hl.indexOf(sk[1]) == -1) hl.push(sk[1])
}
console.log(w * h - (w - wl.length) * (h - hl.length) - n)