Problem:
Score : 200 points

Problem Statement

There is a rectangle in the xy-plane, with its lower left corner at (0, 0) and its upper right corner at (W, H). Each of its sides is parallel to the x-axis or y-axis. Initially, the whole region within the rectangle is painted white.

Snuke plotted N points into the rectangle. The coordinate of the i-th (1 ≦ i ≦ N) point was (x_i, y_i).

Then, he created an integer sequence a of length N, and for each 1 ≦ i ≦ N, he painted some region within the rectangle black, as follows:

If a_i = 1, he painted the region satisfying x < x_i within the rectangle.

If a_i = 2, he painted the region satisfying x > x_i within the rectangle.

If a_i = 3, he painted the region satisfying y < y_i within the rectangle.

If a_i = 4, he painted the region satisfying y > y_i within the rectangle.

Find the area of the white region within the rectangle after he finished painting.

Constraints

1 ≦ W, H ≦ 100

1 ≦ N ≦ 100

0 ≦ x_i ≦ W (1 ≦ i ≦ N)

0 ≦ y_i ≦ H (1 ≦ i ≦ N)

W, H (21:32, added), x_i and y_i are integers.

a_i (1 ≦ i ≦ N) is 1, 2, 3 or 4.

Input

The input is given from Standard Input in the following format:

W H N
x_1 y_1 a_1
x_2 y_2 a_2
:
x_N y_N a_N

Output

Print the area of the white region within the rectangle after Snuke finished painting.

Sample Input 1

5 4 2
2 1 1
3 3 4

Sample Output 1

9

The figure below shows the rectangle before Snuke starts painting.

First, as (x_1, y_1) = (2, 1) and a_1 = 1, he paints the region satisfying x < 2 within the rectangle:

Then, as (x_2, y_2) = (3, 3) and a_2 = 4, he paints the region satisfying y > 3 within the rectangle:

Now, the area of the white region within the rectangle is 9.

Sample Input 2

5 4 3
2 1 1
3 3 4
1 4 2

Sample Output 2

0

It is possible that the whole region within the rectangle is painted black.

Sample Input 3

10 10 5
1 6 1
4 1 3
6 9 4
9 4 2
3 1 3

Sample Output 3

64

Solution in C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

typedef struct xyz{
    int x;
    int y;
    int a;
}c;
int main (void)
{
    int W,H,N;
    int i,j,k;
    int sum = 0;
    int sum1 = 0;
    int s[100][100] = {0};
    struct xyz c[100] ={0};
    scanf("%d",&W);    
    scanf("%d",&H);    
    scanf("%d",&N);  

    for(i=0;i<N;i++){
        scanf("%d",&c[i].x);    
        scanf("%d",&c[i].y);    
        scanf("%d",&c[i].a);  
    }
    for(i=0;i<N;i++){
        if(c[i].a == 1){
            for(j=1;j<=c[i].x;j++){
                for(k=1;k<=H;k++){
                    s[j][k] = 1;
                }
            }
        }
       if(c[i].a == 2){
            for(j=c[i].x +1;j <= W;j++){
                for(k=1;k<=H;k++){
                    s[j][k] = 1;
                }
            }
        }
        if(c[i].a == 3){
            for(j=1;j<=W;j++){
                for(k=1;k<=c[i].y ;k++){
                    s[j][k] = 1;
                }
            }
        }
        if(c[i].a == 4){
            for(j=1;j<=W;j++){
                for(k=c[i].y +1 ; k <= H; k++){
                    s[j][k] = 1;
                }
            }
        }
    }
    
    for(i=1;i<=W;i++){
        for(j=1;j<=H;j++){
            if(s[i][j] == 0)
                sum1++;
        }
    }
    if(sum1 > 0)
        printf("%d\n",sum1);
    else
        puts("0");
return 0;
}