local ior = io.input()
local w, h, n = ior:read("*n", "*n", "*n")
local s, t = {}, {}
for i = 1, n do
  local a, b = ior:read("*n", "*n")
  s[a], t[b] = true, true
end
local snum, tnum = 0, 0
for k, v in pairs(s) do
  snum = snum + 1
end
for k, v in pairs(t) do
  tnum = tnum + 1
end
print(w * h - n - (w - snum) * (h - tnum))