n, m, k = map(int, input().split())
x = k+1
y = k+1
a = []
for i in range(k):
    ri, ci = map(int, input().split())
    a.append([ri, ci])
for i in range(2):
    for j in range(k-1):
        if (a[0][j]-a[0][j+1] == 0) or (a[0][j]-a[0][j+1] == 1):
            x = x-1
for i in range(2):
    for j in range (k-1):
        if (a[1][j]-a[1][j+1] == 0) or (a[1][j]-a[1][j+1] == 1):
            y = y-1
print(x*y)