how to add the lines of differnt files in a single file

Shell Programming and Scripting
1

My question is

I am finding the new.txt file in the directory
I am finding current.txt file in the directory in 2nd time
I am finding fallback.txt in the directory in 3rd time

all with find command

now my question is

let suppose I got all threee files in one directory then I want that output goes into one file and it format shoud be
e.g:
nitin new.txt current.txt fallback.txt {nitin should not display htree time because all three files in same directory}

and if any one file miss(all above three) then that should not comes in final file

2

use

cat file1 file2 file3 >> final_file.txt
3

its append the line in a file

stp2int1 app stpbatch new.txt
stp2int4 web tag new.txt
stp2perf4 app stpmon new.txt
stp2int1 app stpbatch cuurent.txt
stp2int4 web tag new.txt
stp2perf4 app stpmon fallback.txt
stp2int1 app stpbatch fallback.txt
stp2int4 web tag new.txt
stp2perf4 app stpmon fallback.txt

see here stp2int1 has all three files so it should come in the final file and rest of all has missed one file from three so that shuld not come in the final file

its like stp2int1 app stpbatch new.txt current.txt fallback.txt