#include <iostream>
#include <algorithm>
using namespace std;
 
int main() {
    int x_max, y_max, n, a=0, b=0;
    cin>>x_max>>y_max>>n;
    int *x=new int[n+2];
    int *y=new int[n+2];
    for(int i=1;i<n+1;i++) 
       cin>>x[i]>>y[i];
    x[0] = y[0] = 0;
    x[n+1] = x_max + 1; 
    y[n+1] = y_max + 1;
    sort(x, x + n+1);
    sort(y, y + n+1);
    for(int i=0; i<n+1; i++){ 
        if(x[i+1]-x[i]>a) a=x[i+1]-x[i];
	if(y[i+1]-y[i]>b) b=y[i+1]-y[i];
    }
    cout<<(a-1)*(b-1);
    return 0;
}

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MTAgMTAgMwoxIDEKMiAyCjMgMw==

10 10 3
1 1
2 2
3 3