import java.util.Optional;
import java.util.Scanner;

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

	private void solveB() {
		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();
		}

		final int VERTEX_NUM = 2 * N + 2;
		final int SOURCE = 0;
		final int TARGET = VERTEX_NUM - 1;
		int ans = 0;
		Graph graph = new ArrayGraph(VERTEX_NUM);
		for (int i = 0; i < N; i++) {
			graph.link(SOURCE, i+1, B[i]);
			graph.link(i+1, N+i+1, B[i] + C[i]);
			graph.link(N+i+1, TARGET, C[i]);
			ans += B[i] + C[i];
		}
		for (int i = 0; i < M; i++) {
			graph.link(N+1+D[i], 1+E[i], Integer.MAX_VALUE / 3);
		}

		int limitDepth = 0;
		while (isExistFlow(graph, SOURCE, TARGET)) {
			int currentFlow = flow(graph, SOURCE, TARGET, Integer.MAX_VALUE / 3, 0, limitDepth);
			ans -= currentFlow;
			if (currentFlow == 0) {
				limitDepth++;
			}
		}
		System.out.println(ans);
	}

	/*
	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++) {
			costGraph[0][i+1] = B[i];
			costGraph[i+1][N+i+1] = B[i] + C[i];
			costGraph[N+i+1][2*N+1] = C[i];
			ans += B[i] + C[i];
		}
		for (int i = 0; i < M; i++) {
			costGraph[N+1+D[i]][1+E[i]] = Integer.MAX_VALUE / 3;
		}
		int current;
		int limitDepth = 3;
		int[] ansArray = new int[13];
		ansArray[0] = ansArray[1] = ansArray[2] = ans;
		do {
			ansArray[limitDepth] = ans;
			//current = flow(costGraph, 0, Integer.MAX_VALUE / 3, 2 * N + 2, 0, limitDepth, 0);
			ans -= current;
			if (current == 0) {
				limitDepth++;
			}
			System.err.println(limitDepth + ":" + ans);
		} while (limitDepth <= 12 && (ansArray[0] == ans || (ansArray[limitDepth - 3] != ans)));
		// 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;
		}
		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;
					return tmpFlow;
				}
			}
		}
		return 0;
	}
	*/

	interface Graph {
		void link(int from, int to, int cost);
		Optional<Integer> getCost(int from, int to);
		int getVertexNum();
	}

	class ArrayGraph implements Graph {
		private Integer[][] costArray;
		private int vertexNum;

		public ArrayGraph(int n) {
			costArray = new Integer[n][];
			for (int i = 0; i < n; i++) {
				costArray[i] = new Integer[n];
			}
			vertexNum = n;
		}

		@Override
		public void link(int from, int to, int cost) {
			costArray[from][to] = new Integer(cost);
		}

		@Override
		public Optional<Integer> getCost(int from, int to) {
			return Optional.ofNullable(costArray[from][to]);
		}

		@Override
		public int getVertexNum() {
			return vertexNum;
		}
	}

	private int maxFlow(Graph graph) {
		return 0;
	}

	private int flow(Graph graph, int from, int to, int current_flow, int depth, int limitDepth) {
		if (from == to) {
			return current_flow;
		}
		if (depth >= limitDepth) {
			return 0;
		}
		for (int id = 0; id < graph.getVertexNum(); id++) {
			Optional<Integer> cost = graph.getCost(from, id);
			if (cost.orElse(0) > 0) {
				int nextFlow = current_flow < cost.get() ? current_flow : cost.get();
				int returnFlow = flow(graph, id, to, nextFlow, depth+1, limitDepth);
				if (returnFlow > 0) {
					graph.link(from, id, cost.get() - returnFlow);
					graph.link(id, from, graph.getCost(id, from).orElse(0) + returnFlow);
					return returnFlow;
				}
			}
		}
		return 0;
	}

	private boolean isExistFlow(Graph graph, int from, int to) {
		boolean[] passed = new boolean[graph.getVertexNum()];
		return search(graph, from, to, passed);
	}

	private boolean search(Graph graph, int from, int to, boolean[] passed) {
		if (from == to) {
			return true;
		}
		passed[from] = true;
		for (int id = 0; id < graph.getVertexNum(); id++) {
			if (!passed[id] && graph.getCost(from, id).orElse(0) > 0 && search(graph, id, to, passed)) {
				return true;
			}
		}
		return false;
	}
}