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

const int N=100005;
const int INF=0x3f3f3f3f;
int n,m,q,a[N],b[N];
int mina=INF,minb=INF,ans;

int main()
{
	scanf("%d%d%d",&n,&m,&q);
	for(int i=1;i<=n;i++) scanf("%d",&a[i]),mina=min(mina,a[i]);
	for(int i=1;i<=m;i++) scanf("%d",&b[i]),minb=min(minb,b[i]);
	ans=mina+minb;
	while(q--)
	{
		int x,y,c;
		scanf("%d%d%d",&x,&y,&c);
		ans=min(ans,a[x]+b[y]-c);
	}
	printf("%d\n",ans);
}