function Main(input) {
  "use strict";
	const lines = input.split("\n");
  let nums = lines.map(s => parseInt(s, 10));
  nums.pop()
  const k = nums.pop();

  let n ;
  while (n = nums.shift()) {
    if (!nums.every(x => Math.abs(n - x) <= k)) {
      break;
    }
  }
	//出力
  console.log( n === undefined ? "Yay!" : ":(")
}
// Exec
Main(require("fs").readFileSync("/dev/stdin", "utf8"));