use std::io::*;
use std::str::FromStr;
//use std::num;
//use std::cmp;
//use std::collections::VecDeque;

fn main() {
	let mut s: Vec<char> = read_array();
	let mut flag = 0;

	if s.len() % 2 == 0 {
		for _i in 0..s.len() / 2 {
			if s[_i] == s[s.len() / 2 + _i] {
				flag = 1;
			}
		}
	}

	if flag == 0 {
		print!("NO");
	} else {
		print!("YES");
	}
}

pub fn my_floor(x: f64) -> f64 {
	let rounded = (x * 1000.0).floor() / 1000.0;

	rounded
}

pub fn upper_lower(x: char) -> char {
	let result: char;

	if x.is_uppercase() {
		result = x.to_ascii_lowercase();
	} else if x.is_lowercase() {
		result = x.to_ascii_uppercase();
	} else {
		result = x;
	}

	result
}

pub fn max_2(x: usize, y: usize) -> usize {
	let result;

	if x >= y {
		result = x;
	} else {
		result = y;
	}

	result
}

pub fn max_3(x: isize, y: isize, z: isize) -> isize {
	let result;
	if x >= y && y >= z {
		result = x;
	} else if x >= z && z >= y {
		result = x;
	} else if y >= x && x >= z {
		result = y;
	} else if y >= z && z >= x {
		result = y;
	} else if z >= x && x >= y {
		result = z;
	} else {
		result = z;
	}

	result
}

pub fn min_3(x: isize, y: isize, z: isize) -> isize {
	let result;
	if x <= y && y <= z {
		result = x;
	} else if x <= z && z <= y {
		result = x;
	} else if y <= x && x <= z {
		result = y;
	} else if y <= z && z <= x {
		result = y;
	} else if z <= x && x <= y {
		result = z;
	} else {
		result = z;
	}

	result
}

pub fn read_line() -> String {
	let mut s: String = String::new();
	std::io::stdin().read_line(&mut s).ok();

	s
}

pub fn read<T: FromStr>() -> T {
	let stdin = stdin();
	let stdin = stdin.lock();
	let token: String = stdin
		.bytes()
		.map(|c| c.expect("failed to read char") as char)
		.skip_while(|c| c.is_whitespace())
		.take_while(|c| !c.is_whitespace())
		.collect();
	token.parse().ok().expect("failed to parse token")
}

pub fn read_array() -> Vec<char> {
	let array: String = read();
	let chars: Vec<char> = array.trim().chars().collect::<Vec<char>>();
	chars
}

pub fn get_data() -> Vec<u64> {
	let mut s: String = String::new();
	std::io::stdin().read_line(&mut s).ok();
	let vec: Vec<u64> = s
		.trim()
		.split_whitespace()
		.map(|e| e.parse().ok().unwrap())
		.collect();

	vec
}

pub fn get_chars() -> Vec<char> {
	let mut s: String = String::new();
	std::io::stdin().read_line(&mut s).ok();

	let vec: Vec<char> = s.trim().chars().collect::<Vec<char>>();

	vec
}