#include <bits/stdc++.h>
#define int long long
using namespace std;
struct node{
	int a,b;
}arr[100050],brr[100050];
int n,m,l,ans;
signed main(){
	cin>>l>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>arr[i].a>>arr[i].b;
	}
	for(int i=1;i<=m;i++){
		cin>>brr[i].a>>brr[i].b;
	}
	int j=1;
	for(int i=1;i<=n && j<=m;){
		int minn=min(arr[i].b,brr[j].b);
		if(arr[i].a==brr[j].a){
			ans+=minn;
		}
		arr[i].b-=minn;
		brr[j].b-=minn;
		if(brr[j].b<=0){
			j++;
		}
		if(arr[i].b<=0){
			i++;
		}
	}
	cout<<ans;
}

I2luY2x1ZGUgPGJpdHMvc3RkYysrLmg+CiNkZWZpbmUgaW50IGxvbmcgbG9uZwp1c2luZyBuYW1lc3BhY2Ugc3RkOwpzdHJ1Y3Qgbm9kZXsKCWludCBhLGI7Cn1hcnJbMTAwMDUwXSxicnJbMTAwMDUwXTsKaW50IG4sbSxsLGFuczsKc2lnbmVkIG1haW4oKXsKCWNpbj4+bD4+bj4+bTsKCWZvcihpbnQgaT0xO2k8PW47aSsrKXsKCQljaW4+PmFycltpXS5hPj5hcnJbaV0uYjsKCX0KCWZvcihpbnQgaT0xO2k8PW07aSsrKXsKCQljaW4+PmJycltpXS5hPj5icnJbaV0uYjsKCX0KCWludCBqPTE7Cglmb3IoaW50IGk9MTtpPD1uICYmIGo8PW07KXsKCQlpbnQgbWlubj1taW4oYXJyW2ldLmIsYnJyW2pdLmIpOwoJCWlmKGFycltpXS5hPT1icnJbal0uYSl7CgkJCWFucys9bWlubjsKCQl9CgkJYXJyW2ldLmItPW1pbm47CgkJYnJyW2pdLmItPW1pbm47CgkJaWYoYnJyW2pdLmI8PTApewoJCQlqKys7CgkJfQoJCWlmKGFycltpXS5iPD0wKXsKCQkJaSsrOwoJCX0KCX0KCWNvdXQ8PGFuczsKfQ==

MTAwMCA0IDcKMTkgNzkKMzMgNDYzCjE5IDE3OAozMyAyODAKMTkgMjU1CjMzIDkyCjM0IDI1CjE5IDk2CjEyIDExCjE5IDQ5MAozMyAzMQ==

1000 4 7
19 79
33 463
19 178
33 280
19 255
33 92
34 25
19 96
12 11
19 490
33 31