process.stdin.resume();
process.stdin.setEncoding('utf8');

var lines = []
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});

reader.on('line', (line) => {
  lines.push(line);
});

reader.on('close', () => {
    
  var N = lines[0];
  let len = parseInt(N.length)
  let result = 'NO';
  let firstHalf = N.slice(0,len/2)
  let secondHalf = N.slice(len/2, len)
   
  if(firstHalf == secondHalf){
   result = 'YES';
  }
  console.log(result);
  

});