Hi,
Can anybody tell me how to solve this problem with less memory because I managed to solve it but with more than 5000KB.

Why do you use so much memory:)
You just need array for 256K/2 64 bit numbers
So 256*1024*8/2 = 1 MB

Another variant is parsing text from then end (256Kb)

Ha, I see, i juse link-data structure.
we just need to store the input text, don't we?

Link-data structure :) is it joke

just read all numbers to static array and out this from the end

or

read whole text and extract numbers starting from
the end