import java.util.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class ith{
	public static void main(String[] args) throws IOException{
	BufferedReader sc = new BufferedReader(new InputStreamReader(System.in));
	//Scanner sc=new Scanner(System.in);
	while(true){	
	String s = sc.readLine();
	String [] pol = s.split(" ");
	int x=Integer.parseInt(pol[0]);
	int y=Integer.parseInt(pol[1]);
	int pocK=Integer.parseInt(pol[2]);
	
	if ((x==0)&&(y==0)&&(pocK==0))break;
	int[][] pole=new int[pocK][2];
	byte[][] sachovnica=new byte[x][y];
	
	
	for(int i=0;i<pocK;i++){
		String s2 = sc.readLine();
		String [] pol1 = s2.split(" ");
		pole[i][1]=Integer.parseInt(pol1[0])-1;
		//System.out.println(pole[i][0]);
		pole[i][0]=Integer.parseInt(pol1[1])-1;
		//System.out.println(pole[i][1]);
	}
	for(int k=0;k<pocK;k++){
		fillX(pole[k][0],x,sachovnica,pole[k][1]);
		fillY(pole[k][1],y,sachovnica, pole[k][0]);
		fillDiagA(x,y,sachovnica,pole[k][1],pole[k][0]);
		fillDiagB(x,y,sachovnica,pole[k][1],pole[k][0]);

		
		//System.out.println();
	}
		

		//pisPole(x,y,sachovnica);
		int l =0;
		for(int i=0;i<x;i++){
		for(int j=0;j<y;j++){
		if (sachovnica[i][j] == 0)l++;
		}
		
	}
		System.out.println(l);}
	}

	static void fillX(int a,int x, byte[][] sachovnica, int kry){
		for(int i=0;i<x;i++){
			sachovnica[i][a]=1;
			
		}			
	}

	static void fillY(int b,int y, byte[][] sachovnica, int krx){
		for(int i=0;i<y;i++){
			sachovnica[b][i]=1;
			
		}			
	}
	static void pisPole(int x,int y,byte[][] sachovnica){
	for(int i=0;i<x;i++){
		for(int j=0;j<y;j++){
		System.out.print(sachovnica[i][j]+" ");
		}
		System.out.println();
	}	}
	static void fillDiagA(int x,int y, byte[][] sach, int krx,int kry){
		int pomx = krx ;
		int pomy = kry ;
		while((pomx >= 0) && (pomy>=0))
		{
			sach[pomx][pomy] = 1;
			pomx--;
			pomy--;
	
		}
		
		pomx = krx;
		pomy = kry;		
		while((pomx<x)&&(pomy<y))
		{
			sach[pomx][pomy]=1;
			pomx++;
			pomy++;
		
		}

	}

	static void fillDiagB(int x,int y, byte[][] sach, int krx,int kry){
		int pomx = krx ;
		int pomy = kry ;
		while((pomx < x) && (pomy>=0))
		{
			sach[pomx][pomy] = 1;
			pomx++;
			pomy--;
	
		}
		
		pomx = krx;
		pomy = kry;		
		while((pomx>=0)&&(pomy<y))
		{
			sach[pomx][pomy]=1;
			pomx--;
			pomy++;
		
		}

	}

}