#include <iostream>
#include <cstdio>
#include <string>
#include <sstream>

#include <vector>
#include <deque>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <bitset>
#include <functional>
#include <algorithm>

using namespace std;

typedef unsigned int uint;
typedef unsigned char uchar;
typedef unsigned long long ulonglong;

bool hasInput();
void readInput();
void calculate();
void writeOutput();
void reset();

uint X = 0,Y = 0,N = 0, result = 0;
vector<bool> rows, cols, downDiags, upDiags;

#define ROW(y) (y-1)
#define COL(x) (x-1)
#define DOWNDIAG(x,y,Y) (x-y+Y-1)
#define UPDIAG(x,y) (x-1+y-1)


int main(int argc, char **argv) {
	while (true) {
		reset();
		if (!hasInput())
			break;
		readInput();
		calculate();
		writeOutput();
	}
	return 0;
}

void reset() {
	X = Y = N = result = 0;
}

bool hasInput() {
	cin >> X >> Y >> N;
	return !(X == 0 && Y == 0 && N == 0);
}

void readInput() {
	rows.resize(Y, false);
	cols.resize(X, false);
	downDiags.resize(X+Y-1, false);
	upDiags.resize(X+Y-1, false);
	for (uint q = 0; q < N; ++q) {
		uint x, y;
		cin >> x >> y;
		rows[ROW(y)] = true;
		cols[COL(x)] = true;
		downDiags[DOWNDIAG(x,y,Y)] = true;
		upDiags[UPDIAG(x,y)] = true;
	}
}

void calculate() {
	result = 0;
	for (uint x = 1; x <= X; ++x) {
		for (uint y = 1; y <= Y; ++y) {
			if (!rows[ROW(y)]
				&& !cols[COL(x)]
				&& !downDiags[DOWNDIAG(x,y,Y)]
				&& !upDiags[UPDIAG(x,y)])
					++result;
		}
	}
}

void writeOutput() {
	cout << result << endl;
}