<?php

$N = trim(fgets(STDIN));
$C = trim(fgets(STDIN));
$V = trim(fgets(STDIN));
$S = explode(" ",trim(fgets(STDIN)));
$T = explode(" ",trim(fgets(STDIN)));
$Y = explode(" ",trim(fgets(STDIN)));
$M = explode(" ",trim(fgets(STDIN)));

$ans = move (1, $C, 0, false);
if ($ans == false) {
  echo "-1\n";
} else {
  echo $ans."\n";
}


function move($start, $money, $time, $totalTime) {
  global $N, $V, $S, $T, $Y, $M;

  if ($money < 0) {
    return false;
  } else if ($start == $N) {
    return $time;
  } else if ($totalTime != false && $time >= $totalTime) {
    return false;
  }

  $min = $totalTime;
  for ($i = 0; $i < $V; $i++) {
    if ($start == $S[$i]) {
      $newTime = move($T[$i], $money - $Y[$i], $time + $M[$i], $min);
      if ($newTime == false) {

      } else if ($min == false) {
        $min = $newTime;
      } else {
        $min = min($min, $newTime);
      }
    }
  }

  return $min;
}

?>