import Control.Monad
import Data.List
import Data.Array

main = do
  li <- getLine
  let [a,b,m] = map read $ words li
  li <- getLine
  let as = map read $ words li
  li <- getLine
  let bs = map read $ words li
  xycs <- forM [1..m] (\_ -> do
    li <- getLine
    let [x,y,c] = map read $ words li
    return (x,y,c)
    )
  let ans = compute a as b bs xycs
  print ans

compute :: Int -> [Int] -> Int -> [Int] -> [(Int,Int,Int)] -> Int
compute a as b bs xycs = minimum (naive:discounts)
  where
    naive = minimum as + minimum bs
    aa = listArray (1,a) as
    ba = listArray (1,b) bs
    discounts = [aa ! x + ba ! y - c | (x,y,c) <- xycs]
