<?php
  list($vegCount, $meatCount, $reg, $max) = explode(" ", trim(fgets(STDIN)));

  $maxVegCount = $vegCount;
  if ($max < $vegCount) {
    $maxVegCount = $max;
  }

  $result = 0;
  for ($i = $maxVegCount; $i >= 0; $i--) {
    if ($i * $reg <= $meatCount && $meatCount + $i <= $max) {
      $result = $i;
      break;
    }
  }

  printf("$result");