#include<stdio.h>
#include<stdlib.h>
int main()
{
	int i, n, m, b, g, x, y, k, j, count = 0;
	scanf("%d", &n);
	scanf("%d", &m);
	scanf("%d", &b);
	scanf("%d", &g);
	int** a;
	a = (int**)malloc(n * sizeof(int));
	for (i = 0; i < n; i++) {
		a[i] = (int*)malloc(m * sizeof(int));
	}
	for (i = 0; i < n; i++) {
		for (j = 0; j < m; j++) {
			a[i][j] = 0;
		}
	}
	for (i = 0; i < b; i++) {
		scanf("%d", &x);
		scanf("%d", &y);
		for (j = x - 1; j <= y - 1; j++) {
			for (k = 0; k < m; k++) {
				a[j][k] = 1;
			}
		}
	}
	for (i = 0; i < g; i++) {
		scanf_s("%d", &x);
		scanf_s("%d", &y);
		for (j = x - 1; j < y; j++) {
			for (k = 0; k < n; k++) {
				a[k][j] = 1;
			}
		}
	}

	for (i = 0; i < n; i++) {
		for (j = 0; j < m; j++) {
			if (a[i][j] == 1) {
				count++;
			}

		}
	}
	printf("%d", count);
	for(i=0;i<n;i++){
	free(a[i]);
	}
	free(a);
	return 0;
}