I didn't understand input=input+i+1

#1

input is a whole string, “i” is a index and 1 is a int.
???

#2

@premang hey,this is called pointer arithmetic,initially input pointer was pointing towards starting of string and now we want to make it i+1 steps forward so just add i+1 steps to input ,it will now point to i+1 index forward.Hope you get it.