import java.io.*;

public class per{
    per(String ipStr)throws Exception{//constructor
        start("",ipStr);
    }
    //-----------------------------
    String reverseString(String str)throws Exception{//reverse the string
        String toReturn="";
        for(int i=str.length()-1;i>=0;i--){
           toReturn+=str.substring(i,i+1);
        }return toReturn;
    }
    //-----------------------------
    String swapTwoCharacter(String str,int index)throws Exception{//swap two character
        String toReturn=null;
        if(index0){
            if(str.length()>2){
                char ch_ind = str.charAt(index);//inbetween character
                char ch_start = str.charAt(0);//starting char

                String middle=str.substring(1,index);
                String tail=str.substring(1+index);

                String indexString= new String(new char[]{ch_ind});
                String startString= new String(new char[]{ch_start});

                toReturn=indexString+middle+startString+tail;
            }else if(index3){
           for(int i=0;i