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

int main(){
  int N,M,K;cin >> N >> M >> K;
  vector<int> A(N);
  vector<int> B(M);
  for(int i=0;i<N;i++){
    cin >> A[i];
  }
  for(int i=0;i<M;i++){
    cin >> B[i];
  }
  vector<int> C(K);
  int x,y,c;
  for(int i=0;i<K;i++){
    cin >> x >> y >> c;
    C[i] = A[x-1] + B[y-1] - c;
  }
  sort(A.begin(),A.end());
  sort(B.begin(),B.end());
  sort(C.begin(),C.end());
  cout << min(C[0],A[0]+B[0]) << endl;
}