W=int(input())
H=int(input())
N=int(input())
s=0;
m=[]
n=[]
for i in range(0,N):
    S,K=map(int,input().split())
    if (S not in m) and (K not in n):
        H-=1
        W-=1
        s+=H+W
    elif (S in m) and (K not in n):
        H-=1
        s+=W-1
    elif (K in n) and (S not in m):
        W-=1
        s+=H-1
    else: s-=1
    m.append(S)
    n.append(K)
print(s)