#include <cstdio>
#include <climits>
#include <algorithm>
#include <cstdlib>
#define MAX 22
using namespace std;

struct raton {
    int p, v;
};

struct madriguera {
    int p, c;
};

int n, m, sol, mejorSol = INT_MAX;
raton ratones[MAX];
madriguera hoyos[MAX];

void solve(int i) {
    if (i == n) {
        mejorSol = sol;
        return;
    }
    for (int j = 0; j < m; ++j) {
        if ((ratones[i].v <= hoyos[j].c) && (abs(ratones[i].p-hoyos[j].c) < mejorSol)) {
            int viejo = sol;
            hoyos[j].c -= ratones[i].v;
            sol = max(sol, abs(ratones[i].p-hoyos[j].c));
            solve(i+1);
            sol = viejo;
            hoyos[j].c += ratones[i].v;
        }
    }
}

bool compareR(raton lhs, raton rhs) { return lhs.p < rhs.p; }
bool compareH(madriguera lhs, madriguera rhs) { return lhs.p < rhs.p; }

int main () {
    scanf("%d", &n);
    for (int i = 0; i < n; ++i)
        scanf("%d%d", &ratones[i].p, &ratones[i].v);

    scanf("%d", &m);
    for (int i = 0; i < m; i++)
        scanf("%d%d", &hoyos[i].p, &hoyos[i].c);

    sort(ratones, ratones + n, compareR);
    sort(hoyos, hoyos + m, compareH);

    solve(0);

    if(mejorSol == INT_MAX) printf("-1\n");
    else printf("%d\n", mejorSol);
}