import java.io.*;
import java.util.*;

public class ith {

public static void main(String[] args) throws Exception {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

while(true) {
String[] s = br.readLine().split(" ");
int x = Integer.parseInt(s[0]);
int y = Integer.parseInt(s[1]);
int n = Integer.parseInt(s[2]);
if(x == 0 && y == 0 && n == 0) break;

boolean[][] pole = new boolean[x][y];
for(int i = 0; i < x; i++)
for(int j = 0; j < y; j++) {
pole[i][j] = true;
}

for(int k = 0; k < n; k++) {
String[] s2 =  br.readLine().split(" ");
int a = (Integer.parseInt(s2[0]))-1;
int b = (Integer.parseInt(s2[1]))-1;

if(x == y) {
	for(int i = 0; i < x; i++) {
	pole[i][b] = false;
	pole[a][i] = false;
	}
} else if(x < y) {
	for(int i = 0; i < x; i++) {
	pole[i][b] = false;
	pole[a][i] = false;
	}
	for(int i = x; i < y; i++) {
	pole[a][i] = false;
	}
} else if(x > y) {
	for(int i = 0; i < y; i++) {
	pole[i][b] = false;
	pole[a][i] = false;
	}
	for(int i = y; i < x; i++) {
	pole[i][b] = false;
	}
}

int i1 = a;
int i2 = a;
int j = b;
while (i1 < x && i2 >= 0 && j < y){
	pole[i1][j] = false;
	pole[i2][j] = false;
	i1++;
	i2--;
	j++;
}
if(i1 < x) {
	int j2 = j;
	while (i1 < x && j2 < y){
	pole[i1][j2] = false;
	i1++;
	j2++;
	}
}
if(i2 >= 0) {
	int j2 = j;
	while (i2 >= 0 && j2 < y){
	pole[i2][j2] = false;
	i2--;
	j2++;
	}
}

i1 = a;
i2 = a;
j = b;
while (i1 < x && i2 >= 0 && j >= 0) {
	pole[i1][j] = false;
	pole[i2][j] = false;
	i1++;
	i2--;
	j--;
}
if(i1 < x) {
	int j2 = j;
	while (i1 < x && j2 >= 0){
	pole[i1][j2] = false;
	i1++;
	j2--;
	}
}
if(i2 >= 0) {
	int j2 = j;
	while (i2 >= 0 && j2 >= 0){
	pole[i2][j2] = false;
	i2--;
	j2--;
	}
}

}
int count = 0;
for(int i = 0; i < x; i++) {
for(int j = 0; j < y; j++) {
if(pole[i][j]) count++;
}
}
System.out.println(count);


}
}

}