Whats the error in the code its not running

#1
#2

hello @anantgovil123
u can not use indexing on empty string b( yeah b is empty ).

do this->
declare ur b string with size same as a and then u can use indexing

#3

i did that i am getting wrong output could u tell the mistake https://ide.codingblocks.com/s/346543

#4

check now