#include "robots.h"
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;

//#define ok 
//#define int long long
#define ll long long
#define fi first
#define se second
#define pb push_back
#define mp make_pair

typedef pair<int, int> ii;
typedef pair<ii, int> iii;
typedef pair<ii, ii> iiii;

const int N = 3e5 + 5;

const int oo = 1e18 + 7, mod = 1e9 + 7;

mt19937 rng(1);

int rnd(int l, int r){
	int temp = rng() % (r - l + 1);
	return abs(temp) + l;
}

int a, b, t;
int x[N], y[N];
// w[N], s[N];
ii obj[N];

bool ck(int xx){
	priority_queue<int, vector<int>> pq;
	int itr = 0;
	for(int i = 0; i < a; i++){
		while(itr < t && obj[itr].fi < x[i]){
			pq.push(obj[itr].se);
			itr++;	
		}
		for(int j = 0; j < xx; j++){
			if(pq.empty()) break;
			pq.pop();	
		}
	}
	while(itr < t){
		pq.push(obj[itr].se);
		itr++;
	}
	for(int i = b - 1; i >= 0; i--){
		if(!pq.empty() && pq.top() >= y[i]) return 0;
		for(int j = 0; j < xx; j++){
			if(pq.empty()) break;
			pq.pop();
		}
	}
	return (pq.empty());
}

int putaway(int A, int B, int T, int X[], int Y[], int W[], int S[]){
	a = A, b = B, t = T;
	for(int i = 0; i < a; i++) x[i] = X[i];
	for(int i = 0; i < b; i++) y[i] = Y[i];
	sort(x, x + a);
	sort(y, y + b);
	for(int i = 0; i < t; i++){
		obj[i] = {W[i], S[i]};
		if(obj[i].fi >= x[a - 1] && obj[i].se >= y[b - 1]) return -1;
	}
	sort(obj, obj + t);
	int l = 0, r = t;
//	if(!ck(t)) return -1;
	while(l < r){
		int mid = (l + r) >> 1;
		if(!ck(mid)) l = mid + 1;
		else r = mid;
	}
	return l;
}

#ifdef ok

void process(){
	int a, b, t, x[1005], y[1005], w[1005], s[1005];
	//exit(0);
	cin >> a >> b >> t;
//	cout << a << " " << b << " " << t << "\n";
//	exit(0);
	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";
}

signed main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	process();
}
#endif