import java.lang.Math.*
import java.util.*

fun main(args: Array<String>) {
    val scn = Scanner(System.`in`)
    var A = scn.nextInt()
    var B = scn.nextInt()
    var M = scn.nextInt()

    var a = IntArray(A+1)
    var b = IntArray(B+1)
    var minA = 1000000
    for(i in 1..A){
        a[i] = scn.nextInt()
        minA = min(minA, a[i])
    }
    var minB = 1000000
    for(i in 1..B){
        b[i] = scn.nextInt()
        minB = min(minB, b[i])
    }

    var min = minA + minB
    for(m in 1..M){
        val x = scn.nextInt()
        val y = scn.nextInt()
        val c = scn.nextInt()

        var sum = a[x] + b[y] - c
        min = min(min,sum)
    }
    println(min)
}