Error? NZEC

This gives me that NZEC error and I don’t know what I did wrong.

`//Java program to show the use of Split method (Before Java 8)

import java.util.Scanner;

public class tictactoe {

public static void main(String[] args) {

    Scanner input = new Scanner(System.in);

    int stringNumber = input.nextInt();

    for (int i = 0; i <= stringNumber; i++) {

        String str = input.next();

        String[] arr = str.split("");

        for(int a=0; a<str.length(); a++){

            if(arr[a].equals("a")){
                arr[a] = "b";
            }
            else if(arr[a].equals("b")){
                arr[a] = "c";
            }
            else if(arr[a].equals("c")){
                arr[a] = "d";
            }
            else if(arr[a].equals("d")){
                arr[a] = "e";
            }
            else if(arr[a].equals("e")){
                arr[a] = "f";
            }
            else if(arr[a].equals("f")){
                arr[a] = "g";
            }
            else if(arr[a].equals("g")){
                arr[a] = "h";
            }
            else if(arr[a].equals("h")){
                arr[a] = "i";
            }
            else if(arr[a].equals("i")){
                arr[a] = "j";
            }
            else if(arr[a].equals("j")){
                arr[a] = "k";
            }
            else if(arr[a].equals("k")){
                arr[a] = "l";
            }
            else if(arr[a].equals("l")){
                arr[a] = "m";
            }
            else if(arr[a].equals("m")){
                arr[a] = "n";
            }
            else if(arr[a].equals("n")){
                arr[a] = "o";
            }
            else if(arr[a].equals("o")){
                arr[a] = "p";
            }
            else if(arr[a].equals("p")){
                arr[a] = "q";
            }
            else if(arr[a].equals("q")){
                arr[a] = "r";
            }
            else if(arr[a].equals("r")){
                arr[a] = "s";
            }
            else if(arr[a].equals("s")){
                arr[a] = "t";
            }
            else if(arr[a].equals("t")){
                arr[a] = "u";
            }
            else if(arr[a].equals("u")){
                arr[a] = "v";
            }
            else if(arr[a].equals("v")){
                arr[a] = "w";
            }
            else if(arr[a].equals("w")){
                arr[a] = "x";
            }
            else if(arr[a].equals("x")){
                arr[a] = "y";
            }
            else if(arr[a].equals("y")){
                arr[a] = "z";
            }

        }

        for(int j=0; j<str.length(); j++){
            System.out.print(arr[j]);
        }

        System.out.println();
    }

}

}
`

for java code you have to use class name as Codechef