import java.util.Scanner

fun main(args: Array<String>) {
	val scn = Scanner(System.`in`)
	val a = scn.nextInt()
	val b = scn.nextInt()
	val m = scn.nextInt()
	val fs = IntArray(a){scn.nextInt()}
	val ms = IntArray(b){scn.nextInt()}
	var min = fs.min()!! + ms.min()!!
	repeat(m){
		val fr = fs[scn.nextInt()-1]
		val mw = ms[scn.nextInt()-1]
		min = Math.min(min, fr+mw-scn.nextInt())
	}
	print(min)
}