#include<stdio.h>
int mp[1000][1000]={0};
int main()
{
	int i,j,q,m,n,x1,x2,y1,y2,wn,dt,x,y;
	freopen("deleteit.in","r",stdin);
	freopen("deleteit.out","w",stdout);
	scanf("%d %d %d",&n,&m,&q);
	for (i=0;i<n;i++)
	{
		for (j=0;j<m;j++)
		{
			mp[i][j]=1;
		}
	}
	wn=m*n;
	for (i=0;i<q;i++)
	{
		scanf("%d %d %d %d",&x1,&y1,&x2,&y2);
		
		dt=0;
		for (x=x1;x<=x2;x++)
		{
			for (y=y1;y<=y2;y++)
			{
				if (mp[x][y]==1)
				{
					dt++;
				}
			}
		}
		wn=wn-dt;
		for (x=n-1;x>=0;x--)
		{
			for (y=m-1;y>=0;y--)
			{
				if (mp[x][y]==1) mp[x][y]=!mp[x][y];
				dt--;
				if (dt==0) break;
			}
			if (dt==0) break;
		}
		
	}
	printf("%d",wn);
	
	fclose(stdin);
	fclose(stdout);
	return 0;
}