using namespace std;
int n,m,b,g,x,y,ans;
bool vis[5005][5005];
int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>n>>m>>b>>g;
	for(int i=1;i<=b;++i){
		cin>>x>>y;
		for(int j=1;j<=n;++j){
			for(int k=x;k<=y;++k)vis[k][j]=1;
		}
	}
	for(int i=1;i<=g;++i){
		cin>>x>>y;
		for(int j=1;j<=m;++j){
			for(int k=x;k<=y;++k)vis[j][k]=1;
		}
	}
	for(int i=1;i<=n;++i){
		for(int j=1;j<=m;++j){
			if(vis[i][j])ans++;
		}
	}
	cout<<ans;
	return 0;
} ```