if(!Array.prototype.unshift) {
  function array_unshift() {
  	this.reverse();
  	for(var i=arguments.length-1; i>=0; i--){
      	this[this.length] = arguments[i];
  	}
  	this.reverse();
  	return this.length
  }
  Array.prototype.unshift = array_unshift;
}
if(!Array.prototype.shift) {
	function array_shift() {
    firstElement = this[0];
    this.reverse();
    this.length = Math.max(this.length-1,0);
    this.reverse();
    return firstElement;
  }
  Array.prototype.shift = array_shift;
}
if(!Array.prototype.push) {
  function array_push() {
  	for(var i=arguments.length-1; i>=0; i--){
      this[this.length] = arguments[i];
  	}
  	return this.length
  }
  Array.prototype.push = array_push;
}
if(!Array.prototype.pop) {
	function array_pop() {
    lastElement = this[this.length-1];
    this.length = Math.max(this.length-1,0);
    return firstElement;
  }
  Array.prototype.pop = array_pop;
}