import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map.Entry;
import java.util.PriorityQueue;
import java.util.Scanner;
import java.util.StringTokenizer;

class Main {
    static final int MOD = 1000000007;
    static final int INF = 1 << 30;

    Main() {
        FastScanner sc = new FastScanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        long ans = 0;
        int A = sc.nextInt();
        int B = sc.nextInt();
        int M = sc.nextInt();
        int[] a = new int[A];
        int[] b = new int[B];
        int amin = INF;
        int bmin = INF;
        for(int i=0;i<A;i++){
            a[i]=sc.nextInt();
            amin = Math.min(amin,a[i]);
        }
        for(int i=0;i<B;i++){
            b[i]=sc.nextInt();
            bmin = Math.min(bmin,b[i]);
        }
        int cmin = INF;
        for(int i=0;i<M;i++){
            int x = sc.nextInt()-1;
            int y = sc.nextInt()-1;
            int c = sc.nextInt();
            int cval = a[x] + b[y] - c;
            cmin = Math.min(cmin,cval);
        }
        pw.println(Math.min((amin+bmin),cmin));
        pw.flush();
    }

    public static void main(String[] args) {
        new Main();
    }
}

class FastScanner {
    private BufferedReader reader = null;
    private StringTokenizer tokenizer = null;

    public FastScanner(InputStream in) {
        reader = new BufferedReader(new InputStreamReader(in));
        tokenizer = null;
    }

    public String next() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

    public String nextLine() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                return reader.readLine();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

        return tokenizer.nextToken("\n");
    }

    public long nextLong() {
        return Long.parseLong(next());
    }

    public int nextInt() {
        return Integer.parseInt(next());
    }

    public double nextDouble() {
        return Double.parseDouble(next());
    }

    public ArrayList<Integer> nextIntList(int n) {
        ArrayList<Integer> a = new ArrayList<Integer>(n);
        for (int i = 0; i < n; i++)
            a.add(nextInt());
        return a;
    }

    public ArrayList<Long> nextLongList(int n) {
        ArrayList<Long> a = new ArrayList<Long>(n);
        for (int i = 0; i < n; i++)
            a.add(nextLong());
        return a;
    }
    
    public int[] nextIntArray(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = nextInt();
        return a;
    }

    public long[] nextLongArray(int n) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++)
            a[i] = nextLong();
        return a;
    }
}

Measured memory_bytes: 54056