object Main extends App{
  import scala.io.StdIn.readLine
  import scala.io.StdIn.readInt
  
  val m = readLine.split(" ")(2).toInt
  val a = readLine.split(" ").map(_.toLong)
  val b = readLine.split(" ").map(_.toLong)
  
  val coupons = (1 to m).map(x => readLine).map(_.split(" ").map(_.toInt))
  val buys = coupons.map(x => (a(x(0) - 1) + b(x(1) - 1) - x(2)))
  println( ((a.min+b.min) +: buys).min.toString)
}
