import java.util.*

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val a = sc.nextInt()
    val b = sc.nextInt()
    val m = sc.nextInt()
    val aa = (1..a).map {
      sc.nextInt()
    }
    val bb = (1..b).map {
      sc.nextInt()
    }
    val xyc = (1..m).map {
      Triple(sc.nextInt(), sc.nextInt(), sc.nextInt())
    }

    println(hitachi2020b(aa, bb, xyc))
}

private fun hitachi2020b(aa: List<Int>, bb: List<Int>, xyc: List<Triple<Int, Int, Int>>): Int {
    val prices = mutableListOf<Int>()
    for (xyci in xyc) {
      val x = xyci.first
      val y = xyci.second
      val c = xyci.third
      val ap = aa.get(x - 1)
      val bp = bb.get(y - 1)
      val price = ap + bp - c
      prices.add(price)
    }
    val amin = aa.min()
    val bmin = bb.min()
    val ans = amin!! + bmin!!
    val minPrice = prices.min()!!
    if (ans > minPrice) {
      return minPrice
    }

    return ans
}