def cin():
	return map(int,input().split())

def cino(test=False):
    if not test:
        return int(input())
    else:
        return input()
def cina():
  return list(map(int,input().split()))


a,b,c  = cin()
p = -1
q = 1e9
r = -1
s = 1e9
for i in range(c):
  x,y,z = cin()
  if z==1:
    p = max(x,p)
  elif z==2:
    q = min(x,q)
  elif z==3:
    r = max(r,y)
  else:
    s = min(s,y)

if p==-1:
    p = 0
if q==1e9:
    q = a
if r==-1:
    r=0
if s==1e9:
    s=b

ans = (q-p)*(s-r)
if p>q or r>q:
    print(0)
else:
    print(ans)

