using System; using System.IO; using System.Linq; using System.Text; using System.Collections.Generic; using System.Diagnostics; using System.Numerics; using Enu = System.Linq.Enumerable; class Program { public void Solve() { int N = Reader.Int(); var Val = Reader.IntTable(N); int M = Reader.Int(); var Es = Reader.IntTable(M); int S = N * 2, T = S + 1; var dinic = new Dinic(T + 1); for (int i = 0; i < N; i++) { dinic.AddEdge(S, i, Val[i][0]); dinic.AddEdge(i, N + i, Dinic.INF); dinic.AddEdge(N + i, T, Val[i][1]); } foreach (var e in Es) dinic.AddEdge(e[0], N + e[1], Dinic.INF); int ans = Val.Sum(v => v.Sum()) - dinic.MaxFlow(S, T); Console.WriteLine(ans); } class Dinic { public static readonly int INF = (int)1e9; List[] G; int S, T; int[] level; int[] iter; public Dinic(int V) { G = new List[V]; for (int i = 0; i < V; i++) G[i] = new List(); } public void AddEdge(int from, int to, int capacity) { G[from].Add(new Edge(to, capacity, G[to].Count)); G[to].Add(new Edge(from, 0, G[from].Count - 1)); } public int MaxFlow(int s, int t) { S = s; T = t; int flow = 0; while (true) { BFS(); if (level[T] < 0) return flow; iter = new int[G.Length]; int f; while ((f = DFS(S, INF)) > 0) { flow += f; } } } private void BFS() { level = Enumerable.Repeat(-1, G.Length).ToArray(); Queue que = new Queue(); que.Enqueue(S); level[S] = 0; while (que.Count > 0) { int v = que.Dequeue(); foreach (Edge e in G[v]) if (e.capacity > 0 && level[e.to] < 0) { level[e.to] = level[v] + 1; que.Enqueue(e.to); } } } private int DFS(int v, int flow) { if (v == T) return flow; while (iter[v] < G[v].Count) { Edge e = G[v][iter[v]]; if (e.capacity > 0 && level[v] < level[e.to]) { int d = DFS(e.to, Math.Min(flow, e.capacity)); if (d > 0) { e.capacity -= d; G[e.to][e.reverse].capacity += d; return d; } } iter[v]++; } return 0; } class Edge { public int to, reverse; public int capacity; public Edge(int to, int capacity, int reverse) { this.to = to; this.capacity = capacity; this.reverse = reverse; } } } } class Entry { static void Main() { new Program().Solve(); } } class Reader { private static TextReader reader = Console.In; private static readonly char[] separator = { ' ' }; private static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries; private static string[] A = new string[0]; private static int i; private static void Init() { A = new string[0]; } public static void Set(TextReader r) { reader = r; Init(); } public static void Set(string file) { reader = new StreamReader(file); Init(); } public static bool HasNext() { return CheckNext(); } public static string String() { return Next(); } public static int Int() { return int.Parse(Next()); } public static long Long() { return long.Parse(Next()); } public static double Double() { return double.Parse(Next()); } public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); } public static int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); } public static int[][] IntTable(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); } public static string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); } public static string Line() { return reader.ReadLine().Trim(); } private static string[] Split(string s) { return s.Split(separator, op); } private static string Next() { CheckNext(); return A[i++]; } private static bool CheckNext() { if (i < A.Length) return true; string line = reader.ReadLine(); if (line == null) return false; if (line == "") return CheckNext(); A = Split(line); i = 0; return true; } }