Beijing
China

PALIN

PALIN

Palindrome

PROBLEM

A palindrome is a symmetrical string, that is, a string read identically from left to right
as well as from right to left. You are to write a program which, given a string,
determines the minimal number of characters to be inserted into the string in order to
obtain a palindrome.

As an example, by inserting 2 characters, the string "Ab3bd" can be transformed into
a palindrome ("dAb3bAd" or "Adb3bdA"). However, inserting fewer than 2
characters does not produce a palindrome.

The input file name is PALIN.IN. The first line contains one integer: the length of
the input string N, 3≤N≤5000. The second line contains one string with length N. The
string is formed from uppercase letters from ‘A’ to ‘Z’, lowercase letters from ‘a’ to
‘z’ and digits from ‘0’ to ‘9’. Uppercase and lowercase letters are to be considered
distinct.

The output file name is PALIN.OUT. The first line contains one integer, which is the
desired minimal number.

EXAMPLE INPUT AND OUTPUT

PALIN.IN

PALIN.OUT

5
Ab3bd
2

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출처 IOI 2000