#include<bits/stdc++.h>
using namespace std;
int n,m,k,xz[105],sum;
struct Food{
	int a,b;
}htc[205]; 
int main()
{
	cin>>n>>m>>k;
	for(int i=1;i<=k;i++) cin>>xz[i];
	for(int i=1;i<=n;i++){
		cin>>htc[i].a>>htc[i].b;
		sum+=htc[i].a;
	}
	cout<<sum;
	return 0;
}