// Yukicoder 11 (http://yukicoder.me/problems/30)
#include<cstdio>
#include<set>
#define rep(i,a) for(int i=0;i<(a);++i)

int W, H, N;

int main()
{
	scanf( "%d%d%d", &W, &H, &N );
	
	std::set<int> sw, sh;
	rep( i, N )
	{
		int S, K;
		scanf( "%d%d", &S, &K );

		sw.insert(S);
		sh.insert(K);
	}

	int w = sw.size(), h = sh.size();
	printf( "%d\n", w*H+h*W-w*h-N );

	return 0;
}