import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Main main = new Main();
		main.solveA();
	}

	private void solveA() {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] B = new int[N];
		int[] C = new int[N];
		for (int i = 0; i < N; i++) {
			B[i] = sc.nextInt();
			C[i] = sc.nextInt();
		}
		int M = sc.nextInt();
		int[] D = new int[M];
		int[] E = new int[M];
		for (int i = 0; i < M; i++) {
			D[i] = sc.nextInt();
			E[i] = sc.nextInt();
		}
		int ans = 0;

		// 0=s 2*N+1=t
		Integer[][] costGraph = new Integer[2*N+2][];
		for (int i = 0; i < 2*N+2; i++) {
			costGraph[i] = new Integer[2*N+2];
		}
		for (int i = 0; i < N; i++) {
			int small = B[i] < C[i] ? B[i] : C[i];
			costGraph[0][i+1] = B[i] - small;
			costGraph[i+1][N+i+1] = B[i] + C[i] - small;
			costGraph[N+i+1][2*N+1] = C[i] - small;
			ans += B[i] + C[i] - small;
		}
		for (int i = 0; i < M; i++) {
			costGraph[N+1+D[i]][1+E[i]] = Integer.MAX_VALUE / 3;
		}
		int current;
		int limitDepth = 0;
		boolean changed = false;
		boolean prevChanged = false;
		do {
			current = flow(costGraph, 0, Integer.MAX_VALUE / 3, 2 * N + 2, 0, limitDepth, 0);
			ans -= current;
			if (current == 0) {
				if (changed && !prevChanged) {
					break;
				}
				limitDepth++;
				prevChanged = false;
			} else {
				prevChanged = true;
				changed = true;
			}
		} while (limitDepth <= 12);
		// 12 > log(1^10) / log(N * 2)

		System.out.println(ans);
	}

	private int flow(Integer[][] graph, int current_id, int current_flow, int max_id, int depth, int limitDepth, int prev) {
		if (current_id == max_id - 1) {
			return current_flow;
		}
		if (depth >= limitDepth) {
			return 0;
		}
		int sum_flow = 0;
		for (int id = max_id - 1; id >= 0; id--) {
			if (graph[current_id][id] != null && graph[current_id][id] > 0 && prev != id) {
				int nextFlow = current_flow < graph[current_id][id] ? current_flow : graph[current_id][id];
				int tmpFlow = flow(graph, id, nextFlow, max_id, depth+1, limitDepth, current_id);
				if (tmpFlow > 0) {
					graph[current_id][id] -= tmpFlow;
					if (graph[id][current_id] == null) {
						graph[id][current_id] = 0;
					}
					graph[id][current_id] += tmpFlow;
					sum_flow += tmpFlow;
					current_flow -= tmpFlow;
				}
			}
		}
		return sum_flow;
	}
}