import std.stdio, std.string, std.conv; import std.range, std.algorithm, std.array, std.typecons, std.container; import std.math, std.numeric, core.bitop; enum inf = 1_001_001_001; enum infl = 1_001_001_001_001_001_001L; enum mod = 1_000_000_007L; void main() { string s; scan(s); int n = s.length.to!int; if (n & 1) { writeln("NO"); return; } writeln(s[0..n/2]==s[n/2..$] ? "YES" : "NO"); } void scan(T...)(ref T args) { import std.stdio : readln; import std.algorithm : splitter; import std.conv : to; import std.range.primitives; auto line = readln().splitter(); foreach (ref arg; args) { arg = line.front.to!(typeof(arg)); line.popFront(); } assert(line.empty); } void fillAll(R, T)(ref R arr, T value) { static if (is(typeof(arr[] = value))) { arr[] = value; } else { foreach (ref e; arr) { fillAll(e, value); } } }