#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
#define rep(i, n) REP(i, 0, n)
#define REP(i, s, e) for (int i = (s); i < (int)(e); i++)
#define repr(i, n) REPR(i, n, 0)
#define REPR(i, s, e) for (int i = (int)(s - 1); i >= (int)(e); i--)
#define all(r) r.begin(), r.end()
#define rall(r) r.rbegin(), r.rend()

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;

template <typename T, typename U>
T chmax(T& a, const U& b) {
    if (a >= b) return false;
    a = b;
    return true;
}
template <typename T, typename U>
T chmin(T& a, const U& b) {
    if (a <= b) return false;
    a = b;
    return true;
}

void yes_no(bool f, string yes = "Yes", string no = "No") { cout << (f ? yes : no) << "\n"; }

void solve() {
    int n;
    cin >> n;
    const int sz = n + n + 2;
    mf_graph<ll> g(sz);
    int s = sz - 2, t = sz - 1;
    ll sum = 0;
    const ll inf = 1e18;
    rep(i, n) {
        int a, b;
        cin >> a >> b;
        g.add_edge(s, i, a);
        g.add_edge(n + i, t, b);
        g.add_edge(i, n + i, inf);
        sum += a + b;
    }
    int m;
    cin >> m;
    rep(i, m) {
        int a, b;
        cin >> a >> b;
        g.add_edge(a, n + b, inf);
    }
    ll flow = g.flow(s, t);
    ll ans = sum - flow;
    cout << ans << "\n";
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int t = 1;
    // multi-testcase
    // cin >> t;
    rep(ti, t) solve();
    return 0;
}