#define PROBLEM "https://yukicoder.me/problems/no/119"
// ============
#include <atcoder/maxflow>
template <typename T>
class MongeMinCut {
    int n;
    std::vector<int> k;
    std::vector<int> offset;
    int s;
    int t;
    T all;
    atcoder::mf_graph<T> graph;
    T big;
    void add_v(int v, T f0, T f1) {
        if (f0 <= f1) {
            add_0(f0);
            graph.add_edge(s, v, f1 - f0);
        } else {
            add_0(f1);
            graph.add_edge(v, t, f0 - f1);
        }
    }

public:
    MongeMinCut(const std::vector<int> &k, T big)
        : n((int)k.size()),
          k(k),
          offset(n, 0),
          s(0),
          t(0),
          all(0),
          graph(0),
          big(big) {
        for (int i = 0; i < n; ++i) {
            assert(k[i] >= 1);
        }
        for (int i = 0; i < n - 1; ++i) {
            offset[i + 1] = offset[i] + k[i] - 1;
        }
        s = 0;
        for (int i = 0; i < n; ++i) {
            s += k[i];
        }
        t = s + 1;
        graph = atcoder::mf_graph<T>(s + 2);
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < k[i] - 2; ++j) {
                graph.add_edge(offset[i] + j + 1, offset[i] + j, big);
            }
        }
    }
    void add_0(T v) { all += v; }
    void add_1(int i, const std::vector<T> &f) {
        assert(0 <= i && i < n && (int)f.size() == k[i]);
        add_0(f[0]);
        for (int j = 0; j < k[i] - 1; ++j) {
            add_v(offset[i] + j, f[j + 1] - f[j], 0);
        }
    }
    void add_2(int x, int y, std::vector<std::vector<T>> f) {
        assert(0 <= x && x < n);
        assert(0 <= y && y < n);
        assert((int)f.size() == k[x]);
        for (int i = 0; i < k[x]; ++i) {
            assert((int)f[i].size() == k[y]);
        }
        std::vector<T> tmp(k[x]);
        for (int i = 0; i < k[x]; ++i) {
            tmp[i] = f[i][0];
        }
        add_1(x, tmp);
        for (int i = 0; i < k[x]; ++i) {
            for (int j = 0; j < k[y]; ++j) {
                f[i][j] -= tmp[i];
            }
        }
        tmp = f[0];
        add_1(y, tmp);
        for (int i = 0; i < k[x]; ++i) {
            for (int j = 0; j < k[y]; ++j) {
                f[i][j] -= tmp[j];
            }
        }
        for (int i = 0; i < k[x] - 1; ++i) {
            for (int j = 0; j < k[y] - 1; ++j) {
                T val = f[i][j] + f[i + 1][j + 1] - f[i + 1][j] - f[i][j + 1];
                assert(val <= 0);
                add_0(val);
                graph.add_edge(offset[x] + i, offset[y] + j, -val);
                graph.add_edge(s, offset[x] + i, -val);
            }
        }
    }
    std::pair<T, std::vector<int>> solve() {
        T cost = graph.flow(s, t) + all;
        std::vector<bool> cut = graph.min_cut(s);
        std::vector<int> ans(n, 0);
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < k[i] - 1; ++j) {
                if (cut[offset[i] + j]) {
                    ++ans[i];
                }
            }
        }
        return std::pair<T, std::vector<int>>(cost, ans);
    }
};
// ============
// ============
#include <bits/stdc++.h>
#define OVERRIDE(a, b, c, d, ...) d
#define REP2(i, n) for (i32 i = 0; i < (i32)(n); ++i)
#define REP3(i, m, n) for (i32 i = (i32)(m); i < (i32)(n); ++i)
#define REP(...) OVERRIDE(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
#define PER2(i, n) for (i32 i = (i32)(n)-1; i >= 0; --i)
#define PER3(i, m, n) for (i32 i = (i32)(n)-1; i >= (i32)(m); --i)
#define PER(...) OVERRIDE(__VA_ARGS__, PER3, PER2)(__VA_ARGS__)
#define ALL(x) begin(x), end(x)
#define LEN(x) (i32)(x.size())
using namespace std;
using u32 = unsigned int;
using u64 = unsigned long long;
using i32 = signed int;
using i64 = signed long long;
using f64 = double;
using f80 = long double;
using pi = pair<i32, i32>;
using pl = pair<i64, i64>;
template <typename T>
using V = vector<T>;
template <typename T>
using VV = V<V<T>>;
template <typename T>
using VVV = V<V<V<T>>>;
template <typename T>
using VVVV = V<V<V<V<T>>>>;
template <typename T>
using PQR = priority_queue<T, V<T>, greater<T>>;
template <typename T>
bool chmin(T &x, const T &y) {
    if (x > y) {
        x = y;
        return true;
    }
    return false;
}
template <typename T>
bool chmax(T &x, const T &y) {
    if (x < y) {
        x = y;
        return true;
    }
    return false;
}
template <typename T>
i32 lob(const V<T> &arr, const T &v) {
    return (i32)(lower_bound(ALL(arr), v) - arr.begin());
}
template <typename T>
i32 upb(const V<T> &arr, const T &v) {
    return (i32)(upper_bound(ALL(arr), v) - arr.begin());
}
template <typename T>
V<i32> argsort(const V<T> &arr) {
    V<i32> ret(arr.size());
    iota(ALL(ret), 0);
    sort(ALL(ret), [&](i32 i, i32 j) -> bool {
        if (arr[i] == arr[j]) {
            return i < j;
        } else {
            return arr[i] < arr[j];
        }
    });
    return ret;
}
#ifdef INT128
using u128 = __uint128_t;
using i128 = __int128_t;
#endif
[[maybe_unused]] constexpr i32 INF = 1000000100;
[[maybe_unused]] constexpr i64 INF64 = 3000000000000000100;
struct SetUpIO {
    SetUpIO() {
#ifdef FAST_IO
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
#endif
        cout << fixed << setprecision(15);
    }
} set_up_io;
void scan(char &x) { cin >> x; }
void scan(u32 &x) { cin >> x; }
void scan(u64 &x) { cin >> x; }
void scan(i32 &x) { cin >> x; }
void scan(i64 &x) { cin >> x; }
void scan(string &x) { cin >> x; }
template <typename T>
void scan(V<T> &x) {
    for (T &ele : x) {
        scan(ele);
    }
}
void read() {}
template <typename Head, typename... Tail>
void read(Head &head, Tail &...tail) {
    scan(head);
    read(tail...);
}
#define CHAR(...)     \
    char __VA_ARGS__; \
    read(__VA_ARGS__);
#define U32(...)     \
    u32 __VA_ARGS__; \
    read(__VA_ARGS__);
#define U64(...)     \
    u64 __VA_ARGS__; \
    read(__VA_ARGS__);
#define I32(...)     \
    i32 __VA_ARGS__; \
    read(__VA_ARGS__);
#define I64(...)     \
    i64 __VA_ARGS__; \
    read(__VA_ARGS__);
#define STR(...)        \
    string __VA_ARGS__; \
    read(__VA_ARGS__);
#define VEC(type, name, size) \
    V<type> name(size);       \
    read(name);
#define VVEC(type, name, size1, size2)    \
    VV<type> name(size1, V<type>(size2)); \
    read(name);
// ============

int main() {
    I32(n);
    V<i32> b(n), c(n);
    REP(i, n) {
        read(b[i], c[i]);
    }
    I32(m)
    V<pi> edge(m);
    for (auto &[u, v] : edge) {
        read(u, v);
    }
    MongeMinCut<i32> mincut(V<i32>(n, 3), INF);
    REP(i, n) {
        V<i32> f(3, 0);
        f[0] = -b[i];
        f[2] = -c[i];
        mincut.add_1(i, f);
    }
    for (auto [u, v] : edge) {
        VV<i32> f(3, V<i32>(3, 0));
        f[0][2] = INF / m;
        mincut.add_2(u, v, f);
    }
    cout << -mincut.solve().first << '\n';
}