#include <cstdio>
#include <algorithm>
using namespace std;
int main(){
	int n, m, k, x, y, z;
	scanf("%d %d %d", &n, &m, &k);
	int a[n], b[m];
	for (int i = 0; i < n; i++) scanf("%d", &a[i]);
	for (int i = 0; i < m; i++) scanf("%d", &b[i]);
	int ans = *min_element(a, a + n) + *min_element(b, b + n);
	for (int i = 0; i < k; i++){
		scanf("%d %d %d", &x, &y, &z);
		ans = min(ans, a[x - 1] + b[y - 1] - z);
	}
	printf("%d\n", ans);
}