Problems
Square string
Square string
The string s is a square if it has the form AA, where A is some non-empty string. In other words, a square is a string that is a concatenation of two copies of the same non-empty string. For example, the strings "aa", "zqzq" and "treetree" are squares.
Determine if the given string is a square string.
Input data
One string of length no more than 100.
Output data
Print yes if the input string is a square string and no otherwise.
Examples
Input example #1
treetree
Output example #1
yes
Input example #2
aaa
Output example #2
no