w = gets.not_nil!.to_i64
h = gets.not_nil!.to_i64
n = gets.not_nil!.to_i64

s_visited = {} of Int64 => Bool
k_visited = {} of Int64 => Bool
s_cnt = 0_i64
k_cnt = 0_i64

n.times do
  s, k = gets.not_nil!.split.map(&.to_i64)
  
  unless s_visited.has_key?(s)
    s_visited[s] = true
    s_cnt += 1
  end

  unless k_visited.has_key?(k)
    k_visited[k] = true
    k_cnt += 1
  end
end

ans = s_cnt * h + k_cnt * w - s_cnt * k_cnt - n
puts ans