W = int(input())
H = int(input())
N = int(input())
lssk = [list(map(int,input().split())) for i in range(N)]
lsW = [False]*(W+1)
lsH = [False]*(H+1)
for i in range(N):
    w,h = lssk[i][0],lssk[i][1]
    lsW[w] = True
    lsH[h] = True
print(lsW.count(True)*H+lsH.count(True)*W-lsW.count(True)*lsH.count(True)-N)