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"); } } }