My loop is given me twice the results. As I only want it one time. What should I do?

```
for i in 1..length(newStudentNumber) loop
character := SUBSTR(newStudentNumber, i, 1);
newStudentNumber := newStudentNumber || case character
when 'A' then '16'
when 'B' then '17'
when 'C' then '18'
when 'D' then '19'
when 'E' then '20'
when 'F' then '21'
when 'G' then '22'
when 'H' then '23'
when 'I' then '24'
when 'J' then '25'
when 'K' then '26'
when 'L' then '27'
when 'M' then '28'
when 'N' then '29'
when 'O' then '30'
when 'P' then '31'
when 'Q' then '32'
when 'R' then '33'
when 'S' then '34'
when 'T' then '35'
when 'U' then '36'
when 'V' then '37'
when 'W' then '38'
when 'X' then '39'
when 'Y' then '40'
when 'Z' then '41'
else character
end;
end loop;
dbms_output.put_line(newStudentNumber);
```

I hope I am not too vague with this question

Thanks in advance