'use strict'
function Main(input){
  input=input.trim().split(/\s+/).map(x=>x-0);
  var k=input.pop();
  var result=true;
  var i=0;
  while(input[i+1]){
    if(input[i+1]-input[i]>k)
      result=false;
    i++;
  }
  var ans=result?'Yay!':':(';
  console.log(ans);
}

Main(require('fs').readFileSync('/dev/stdin','utf8'));
