Use
inter:=trunc(r*i+0.0000001)-trunc(r*(i-1)-0.0000001);
instead of
inter:=trunc(r*i)-trunc(r*(i-1));

I had the same problem as you. By the way, on my computer I
couldn't find a test where your program would give the
result that differs from the result of my program, and I
can't explain why do we have to use those 0.0000001. By the
way, see problem 1030 - if you try to submit it, you will
face similar problems...

Good luck!

Thank you very much for your help, but I got Accepted jist
making the cicle to (n div 2) insted to n. Although It was
very nice of you to help me - thanks again, if I can I
would help you,too. Bye!