#include<bits/stdc++.h>

using namespace std;

int main(){
    int a,b,m,aa[100010],bb[100010],mm[100010],ans = 10000000;
    cin >> a >> b >> m;
    for(int i = 0;i < a;i++)cin >> aa[i];
    for(int i = 0;i < b;i++)cin >> bb[i];
    for(int i = 0;i < m;i++){
        int x,y,c;cin >> x >>y >> c;
        ans = min(ans,aa[x-1] + bb[y-1] - c);
    }
    sort(aa,aa+a);
    sort(bb,bb+b);
    ans = min(ans,aa[0]+bb[0]);
    cout << ans;
    return 0;
}