#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,m;
	cin>>a>>b>>m;
	int aa[100005] = {0}, bb[100005] = {0}; 
	for(int i = 1; i <= a; i++){
		cin>>aa[i];
	}
	for(int i = 1; i <= b; i++){
		cin>>bb[i];
	}
	int a1,b1,dis;
	int sum = 0x3f3f3f3f;
	for(int i = 1; i <= m; i++){
		cin>>a1>>b1>>dis;
		sum = min(aa[a1] + bb[b1] - dis ,sum);
	}
	sort(aa + 1,aa + 1 + a);
	sort(bb + 1,bb + 1 + b);
	sum = min(aa[1] + bb[1],sum);
	cout<<sum;
	
	return 0;
}