#include <iostream>
#include <cstdio>
#include <fstream>
#include <algorithm>
#include <cstring>
using namespace std;
typedef pair<int, int> PII;
const int N = 2e4 + 10, M = 510;
PII q[M];
int row[N], col[N], dg[N * 10], udg[N * 10];
int n, m, k;
int res;
int flag[N];
int main()
{
	cin>>n>>m>>k;
	
	for (int i=0;i<k;i++)
	{
		int x,y;
		cin>>x>>y;
		q[i].first=x,q[i].second=y;
		row[x]=col[y]=dg[x+y]=udg[y-x+n+m]=1;
	}
	for(int i=1;i<=n;i++)
	{
		if (row[i]) continue;
		
		int sum=m;
		
		for (int j=0;j<k;j++)
		{
			int a=q[j].first,b=q[j].second;
			
			if (flag[b]!= i) sum--;
			flag[b]=i;
			 
			if (a<i)
			{
				if (b-(i-a)>=1)
				{
					if (flag[b-(i-a)]!=i) sum--;
					flag[b-(i-a)]=i;
				}
				if (b+(i-a)<=m)
				{
					if (flag[b+(i-a)]!=i) sum--;
					flag[b+(i-a)]=i;
				}
			}
			if (i<a)
			{
				if (b+(a-i)<=m)
				{
					if (flag[b+(a-i)]!=i) sum--;
					flag[b+(a-i)]=i;
				}				
				if (b-(a-i)>=1)
				{
					if (flag[b-(a-i)]!=i) sum--;
					flag[b-(a-i)]=i;
				}
			}
		}
		
		res+=sum;
	}
	
	cout<<res<<endl;

	return 0;
}