#include <bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define Liny "Yes\n"
#define Linn "No\n"

int A,B,M,ans,x,y,c,t;
int a[100001],b[100001];

int main(){
  cin>>A>>B>>M;
  REP(i,A){ cin>>a[i];}
  REP(i,B){ cin>>b[i];}
  ans = (int)*min_element(a,a+A) + (int)*min_element(b,b+B);
  REP(i,M){
    cin>>x>>y>>c;
    t = a[x-1]+b[y-1]-c;
    if(t<ans){ans=t;}
  }
  cout << ans <<"\n";
}