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Points: 100 (partial)
Time limit: 1.0s
Memory limit: 64M

Problem type
Allowed languages
Ada, BrainF***, C, C#, C++, Dart, Go, Java, JS, Kotlin, Lua, Pascal, Prolog, Python, Swift, VB

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 first line contains one integer: the length of the input string N, 3 \leq N \leq 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 first line contains one integer, which is the desired minimal number.

Input Sample


Output Sample



  • 2
    Osnielfc_07  commented on Sept. 5, 2022, 2:13 a.m.


  • 2
    linkyless  commented on Sept. 3, 2022, 5:13 a.m.

    ¿Con un algoritmo de LCS sale el problema?

  • 2
    jmrh_1  commented on Feb. 7, 2019, 2:58 a.m.

    Hola . En este problema mando la misma solucion al COJ y me da Accepted y aqui RTE . No se que puede pasar!!! . Saludos .

    • 1
      Sniper  commented on Feb. 20, 2019, 2:34 p.m.

      Recuerda que la memoria límite es 64 MB, una matriz de enteros de 5000 X 5000 se pasa de 64 MB.

      • 1
        aniervs  commented on Feb. 21, 2019, 11:45 p.m.

        Yo hice una DP y declaré el arreglo short, puesto que nunca tienes que añadir más de n letras.