#include<iostream>
#include<cstdio>

using namespace std;

const int maxn = 100 + 10;

const int maxm = 1000000 + 100;

int n;
int m;
int q;

int x;
int x1;
int y;
int y1;

int cnt = 0;

bool Ais[maxm] = {0};

int kount;

int main()
{
	freopen("deleteit.in","r",stdin);
	freopen("deleteit.out","w",stdout);
	scanf("%d%d%d",&n,&m,&q);
	cnt = n * m;
	for(int t = 0;t < q ;t ++)
	{
		scanf("%d%d%d%d",&x,&y,&x1,&y1);
		for(int i = x;i <= x1 ;i ++)
		{
			int u = i * m;
			for(int j = y;j <= y1 ;j ++)
			{
				Ais[u + j] = 1;
			}
		}
		kount = 0;
		for(int i = 0;i < cnt ;i ++)
		{
			if(Ais[i] == 0)
			{
				Ais[kount ++] = 0;
			}
		}
		cnt = kount;
	}
	cout<<kount;
	return 0;
}