w = gets.to_i
h = gets.to_i
ans = Array.new(w,-1)
memo = Array.new(h,false)
gets.to_i.times{
    s,k = gets.split.map(&:to_i)
    if ans[s - 1] == -1
        ans[s - 1] = h
    end
    ans[s - 1] -= 1
    memo[k - 1] = true
    }
tmp = memo.count(true)
p ans.map{|x|x == -1 ? tmp : x}.inject(:+)