import sequtils,strutils
var
    W = stdin.readline.parseInt
    H = stdin.readline.parseInt
    mark : array[1..1_000_001,int]
    num : array[1..1_000_001,int]
    ans : int64
    N = stdin.readline.parseInt
    a,b : int
    y,x : int
    flag : bool
(x,y) = (1,1)
for i in 1..N:
    (a,b) = stdin.readline.split.map(parseInt)
    if mark[a] == 0:
        mark[a] = H - y
        if num[b] > 0:
            mark[a] += 1
        x += 1
        flag = true
    else:
        mark[a] -= 1
        flag = false
    if num[b] == 0:
        num[b] = W - x + 1
        y += 1
    else:
        num[b] -= 1
for i in 1..W:
    ans += mark[i].int64
for i in 1..H:
    ans += num[i].int64
echo ans