Snuke's Coloring 2-1

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 (xi,yi).
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 ai=1, he painted the region satisfying x

Constraints
1≤W,H≤100
1≤N≤100
0≤xi≤W (1≤i≤N)
0≤yi≤H (1≤i≤N)
W, H (21:32, added), xi and yi are integers.
ai (1≤i≤N) is 1,2,3 or 4.
输入
The input is given from Standard Input in the following format:
W H N
x1 y1 a1
x2 y2 a2
:
xN yN aN
输出
Print the area of the white region within the rectangle after Snuke finished painting.

样例

5 4 2
2 1 1
3 3 4

样例
9

#include <bits/stdc++.h>
using namespace std;
int w,h,n;
int x1,x2,y3,y4;
int ans;
int xx,yy,op;
int main(){
    cin >> w >> h >> n;
     x2 = w;
     y4 = h;
    while(n--){
        cin >> xx >> yy >> op;
        if(op == 1) x1 = max(xx,x1);
        else if(op == 2) x2 = min(x2,xx);
        else if(op == 3) y3 = max(yy,y3);
        else y4 = min(yy,y4);
    }
    ans = (x2 - x1) * (y4 - y3);
    if((x1 >= x2) || (y3 >= y4)) cout << 0;
    else cout << ans;
}