#include <bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int(i)=0;i<(n);i++)
typedef long long ll;

int main(){
  int A,B,M,ans=1e9;cin>>A>>B>>M;
  vector<int> a(A,0),b(B,0);
  REP(i,A) cin>>a.at(i);
  REP(i,B) cin>>b.at(i);
  REP(i,M){
    int x,y,c;
    cin>>x>>y>>c;x--;y--;
    ans=min(ans,a.at(x)+b.at(y)-c);
  }
  sort(a.begin(),a.end());
  sort(b.begin(),b.end());
  ans=min(ans,a.at(0)+b.at(0));
  cout<<ans;
}