Problem:
Score : 200 points

Problem Statement

Given are a positive integer N and a string S of length N consisting of lowercase English letters.

Determine whether the string is a concatenation of two copies of some string.
That is, determine whether there is a string T such that S = T + T.

Constraints

1 \leq N \leq 100

S consists of lowercase English letters.

|S| = N

Input

Input is given from Standard Input in the following format:

N
S

Output

If S is a concatenation of two copies of some string, print Yes; otherwise, print No.

Sample Input 1

6
abcabc

Sample Output 1

Yes

Let T = abc, and S = T + T.

Sample Input 2

6
abcadc

Sample Output 2

No

Sample Input 3

1
z

Sample Output 3

No

Solution in Pascal (FPC 2.6.2) (judge verdict: Runtime Error)

uses crt;
var a:string;
i,n:integer;
ok:boolean;
begin
clrscr;
read(n);
read(a);
ok:=true;
if length(a) mod 2<>0 then write('no') else begin
for i:=1 to n div 2 do
if a[i]<>a[i+n div 2]     then begin ok:=false;  break;   end;
if ok then write('yes') else write('no');
end;
readln;
end.