function Map() {
 var struct = function(key, value) {
  this.key = key;
  this.value = value;
 }
 
 var put = function(key, value){
  for (var i = 0; i < this.arr.length; i++) {
   if ( this.arr[i].key === key ) {
    this.arr[i].value = value;
    return;
   }
  }
   this.arr[this.arr.length] = new struct(key, value);
 }
 
 var get = function(key) {
  for (var i = 0; i < this.arr.length; i++) {
   if ( this.arr[i].key === key ) {
     return this.arr[i].value;
   }
  }
  return null;
 }
 
 var remove = function(key) {
  var v;
  for (var i = 0; i < this.arr.length; i++) {
   v = this.arr.pop();
   if ( v.key === key ) {
    continue;
   }
   this.arr.unshift(v);
  }
 }
 
 var size = function() {
  return this.arr.length;
 }
 
 var isEmpty = function() {
  return this.arr.length <= 0;
 }

  var getKeySet = function(){
	var keys = new Array();
	for (var i = 0; i < this.arr.length; i++) {
		var v = this.arr[i].key;
		keys[i] = v;
	}
	return keys;
 }

 this.arr = new Array();
 this.get = get;
 this.put = put;
 this.remove = remove;
 this.size = size;
 this.isEmpty = isEmpty;
 this.getKeySet = getKeySet;
}