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; } }