#include <bits/stdc++.h>
using namespace std;
int main(){
int A, B, M, i, ans=2*(1e5); cin >> A >> B >> M;
vector<int> a(A), b(B), x(M), y(M), c(M);
for(i=0; i<A; i++){ cin >> a[i]; }
for(i=0; i<B; i++){ cin >> b[i]; }
for(i=0; i<M; i++){ cin >> x[i] >> y[i]>> c[i]; }  
for(i=0; i<M; i++){ ans=min(ans, a[x[i]-1]+b[y[i]-1]-c[i]); }    
sort(a.begin(), a.end());sort(b.begin(), b.end());
ans=min(ans, a[0]+b[0]);
cout << ans << "\n";
}