#include <bits/stdc++.h>
using namespace std;
#ifdef tabr
#include "library/debug.cpp"
#else
#define debug(...)
#endif
#ifndef tabr
#include "robots.h"
#endif
int putaway(int a, int b, int t, int x[], int y[], int w[], int s[]) {
sort(x, x + a);
sort(y, y + b);
vector<pair<int, int>> z;
for (int i = 0; i < t; i++) {
if (w[i] >= x[a - 1] && s[i] >= y[b - 1]) {
return -1;
}
int z1 = (int) (x + a - upper_bound(x, x + a, w[i]));
int z2 = (int) (y + b - upper_bound(y, y + b, s[i]));
z.emplace_back(z1, z2);
}
sort(z.begin(), z.end());
int low = 0;
int high = t;
while (high - low > 1) {
int mid = (high + low) / 2;
vector<int> c;
priority_queue<int> pq;
for (int i = 0; i < t; i++) {
pq.emplace(z[i].second);
if ((int) pq.size() > mid * 1LL * z[i].first) {
c.emplace_back(pq.top());
pq.pop();
}
}
sort(c.begin(), c.end());
int ok = 1;
int cnt = 0;
for (int i : c) {
cnt++;
if (cnt > mid * 1LL * i) {
ok = 0;
break;
}
}
if (ok) {
high = mid;
} else {
low = mid;
}
}
return high;
}
#ifdef tabr
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int a, b, t, x[100], y[100], w[100], s[100];
cin >> a >> b >> t;
for (int i = 0; i < a; i++) {
cin >> x[i];
}
for (int i = 0; i < b; i++) {
cin >> y[i];
}
for (int i = 0; i < t; i++) {
cin >> w[i] >> s[i];
}
cout << putaway(a, b, t, x, y, w, s) << '\n';
return 0;
}
#endif
