#include<bits/stdc++.h>
using namespace std;

int main() {
	int A, B, M;
	int a[100000], b[100000];
	int s = INT_MAX;
	cin >> A >> B >> M;
	for(int i = 0; i < A; i++)
		cin >> a[i];
	for(int i = 0; i < B; i++)
		cin >> b[i];
	for(int i = 0; i < M; i++) {
		int x, y, c;
		cin >> x >> y >> c;
		s = min(s, a[x-1] + b[y-1] - c);
	}
	s = min(s, *min_element(a, a + A) + *min_element(b, b + B));
	cout << s << endl;
}

