import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws IOException {
        FastReader scan = new FastReader();
        //PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("taming.out")));
        PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
        Task solver = new Task();
        //int t = scan.nextInt();
        int t = 1;
        for(int i = 1; i <= t; i++) solver.solve(i, scan, out);
        out.close();
    }
    static class Task {
        public void solve(int testNumber, FastReader sc, PrintWriter pw) {
        	int a = sc.nextInt();
        	int b = sc.nextInt();
        	int m = sc.nextInt();
        	int min1 =Integer.MAX_VALUE;
        	int min2 =Integer.MAX_VALUE;
        	int[] arr= new int[a];
        	int[] arr2= new int[b];
        	for(int i=0;i<a;i++){
        		arr[i]=sc.nextInt();
        		min1 = Math.min(arr[i],min1);
        	}
        	for(int i=0;i<b;i++){
        		arr2[i]=sc.nextInt();
        		min2 = Math.min(arr2[i],min2);
        	}
        	int ans = min1+min2;
        	for(int i=0;i<m;i++){
        		int t= arr[sc.nextInt()-1]+arr2[sc.nextInt()-1]-sc.nextInt();
        		ans = Math.min(t,ans);
        	}
        	pw.println(ans);
        }

    }
    static class tup implements Comparable<tup>{
        int a, b,c;
        tup(){};
        tup(int a, int b, int c){
            this.a=a;
            this.b=b;
            this.c=c;
        }

        @Override
        public int compareTo( tup o2) {
            return o2.b!=b?Integer.compare(o2.b,b):Integer.compare(o2.a,a);
        }
    }
    static void shuffle(long[] a) {
        Random get = new Random();
        for (int i = 0; i < a.length; i++) {
            int r = get.nextInt(a.length);
            long temp = a[i];
            a[i] = a[r];
            a[r] = temp;
        }
    }
    static void shuffle(int[] a) {
        Random get = new Random();
        for (int i = 0; i < a.length; i++) {
            int r = get.nextInt(a.length);
            int temp = a[i];
            a[i] = a[r];
            a[r] = temp;
        }
    }
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        public FastReader(String s) throws FileNotFoundException {
            br = new BufferedReader(new FileReader(new File(s)));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

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

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

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

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }

}

Measured memory_bytes: 54952