#include<cstdio>
int map[5005][5005];
int maxn,maxm,girl,boy;
int first,last,ans;
int main(int argc,char **argv){
	scanf("%d %d %d %d",&maxn,&maxm,&boy,&girl);
	for(int it=1;it<=boy;it++){
		scanf("%d %d",&first,&last);
		for(int fex=first;fex<=last;fex++){
			for(int line=1;line<=maxm;line++){
				map[fex][line]=1;
			};
			ans+=maxm;
		};
	};
	for(int it=1;it<=girl;it++){
		scanf("%d %d",&first,&last);
		for(int fex=first;fex<=last;fex++){
			for(int line=1;line<=maxn;line++){
				if(!map[line][fex]){
					map[line][fex]=1;
					ans++;
				};
			};
		};
	};
	printf("%d",ans);
	return 0;
};