#include <bits/stdc++.h>
using namespace std;

int INF = numeric_limits<int>::max() / 10;

template <typename T>
class Dinic {
    const T INF;
    struct edge {
        int to;
        T cap;
        int rev;
    };
    vector<vector<edge>> G;
    vector<int> min_cost, iter;
    bool bfs(int s, int t) {
        min_cost.assign(G.size(), -1);
        queue<int> que;
        min_cost[s] = 0;
        que.push(s);
        while (!que.empty() && min_cost[t] == -1) {
            int p = que.front();
            que.pop();
            for (auto& e : G[p]) {
                if (e.cap > 0 && min_cost[e.to] == -1) {
                    min_cost[e.to] = min_cost[p] + 1;
                    que.push(e.to);
                }
            }
        }
        return min_cost[t] != -1;
    }
    T dfs(int idx, const int t, T flow) {
        if (idx == t)
            return flow;
        for (int& i = iter[idx]; i < (int)G[idx].size(); i++) {
            edge& e = G[idx][i];
            if (e.cap > 0 && min_cost[idx] < min_cost[e.to]) {
                T d = dfs(e.to, t, min(flow, e.cap));
                if (d > 0) {
                    e.cap -= d;
                    G[e.to][e.rev].cap += d;
                    return d;
                }
            }
        }
        return 0;
    }
    //
public:
    Dinic(int V) : INF(numeric_limits<T>::max() / T{10}), G(V) {}
    void add_edge(int from, int to, T cap) {
        G[from].emplace_back((edge){to, cap, (int)G[to].size()});
        G[to].emplace_back((edge){from, 0, (int)G[from].size() - 1});
    }
    T max_flow(int s, int t) {
        T flow = 0;
        while (bfs(s, t)) {
            iter.assign(G.size(), 0);
            T f = 0;
            while ((f = dfs(s, t, INF)) > 0)
                flow += f;
        }
        return flow;
    }
};

int main() {
    int N;
    cin >> N;

    Dinic<int> dinic(100);

    int ans = 0;
    for (int i = 0; i < N; i++) {
        int B, C;
        cin >> B >> C;
        ans += B + C;
        dinic.add_edge(90, i, C);
        dinic.add_edge(i + 50, 95, B);
        dinic.add_edge(i, i + 50, INF);
    }

    int M;
    cin >> M;
    while (M--) {
        int D, E;
        cin >> D >> E;
        dinic.add_edge(E, D + 50, INF);
    }

    ans -= dinic.max_flow(90, 95);
    cout << ans << endl;
}