var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});
var obj = null;
var inputFile = [];
reader.on('line', function(input){inputFile.push(input);});
reader.on('close', function(){
  obj = init(inputFile);
  Main();
});
function nextInt(){return myconv(next(),1);}
function nextStrArray(){return myconv(next(),2);}//半角スペース分割
function nextIntArray(){return myconv(next(),4);}//半角スペース + 数値化
function nextCharArray(){return myconv(next(),6);}//1文字分割
function next(){return obj.next();}
function hasNext(){return obj.hasNext();}
function init(input){  
  var returnObj = {
    "list" : input, "index" : 0, "max" : input.length,
    "hasNext" : function(){return (this.index < this.max);},
    "next" : function(){if(!this.hasNext()){throw "ArrayIndexOutOfBoundsException これ以上ないよ";}else{var returnInput = this.list[this.index];this.index++;return returnInput;}}
  };
  return returnObj;
}
function myout(t){console.log(t);}//標準出力
function myerr(t){console.error(t);}//標準エラー出力
//[no]要素の扱い。数値型
//不明値、異常時:引数そのまま返す　1:数値へ変換
//2:半角SPで分割 4:半角SPで分割し、数値配列へ
//6:1文字で分割  7:1文字で分割し、数値配列へ
//8:半角SPで結合 9:改行で結合 0:文字なしで結合
function myconv(i,no){try{switch(no){case 1:return parseInt(i);case 2:return i.split(" ");case 4:return i.split(" ").map((a)=>Number(a));case 6:return i.split("");case 7:return i.split("").map((a)=>Number(a));case 8:return i.join(" ");case 9:return i.join("\n");case 0:return i.join("");default:return i;}}catch(e){return i;}}
function Main(){
  var s = next();
  if(s.length % 2 == 1){
    myout("NO");
  }else{
    var mae = s.slice(0,s.length / 2);
    var ato = s.slice(- (s.length / 2));
    myerr(mae);
    myerr(ato);
    if(mae == ato){
      myout("YES");
    }else{
      myout("NO");
    }
  }
}