function Main(input) {

  var tmp = input.trim().split("\n");
  var array = tmp.slice(0,tmp.length-1);
  var max = parseInt(tmp[tmp.length-1],10);
  array = array.map(val=>parseInt(val,10));
  var success = true;
  
  for(var i=0;i<array.length;i++){
    
    for(var j=0;j<array.length;j++){
      if(i>=j) continue;
      var dist = array[j]-array[i];

      if(max<dist) {
        success=false;    
        break;
      }
    }
  }
  console.log(success?"Yay!":":(")
  
}

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