w, h, n = input().split()              
w, h, n = int(w), int(h), int(n)       
x = []                                 
y = []                                 
a = []                                 
                                       
for _ in range(n):                     
    x_, y_, a_ = input().split()       
    x.append(int(x_))                  
    y.append(int(y_))                  
    a.append(int(a_))                  
W = w                                  
H = h                                  
w_r = w                                
w_l = 0                                
h_u = h                                
h_l = 0                                
for i in range(n):                     
    if a[i] is 1 and x[i]>w_l:         
        w_l = x[i]                     
    if a[i] is 2 and x[i]<w_r:         
        w_r = x[i]                     
    if a[i] is 3 and y[i]>h_l:         
        h_l = y[i]                     
    if a[i] is 4 and y[i]<h_u:         
        h_u = y[i]                     
                                       
ans = (w_r - w_l)*(h_u - h_l)          
if (w_r - w_l) < 0 or (h_u - h_l) < 0: 
    ans = 0                            
print(ans)                             
