1. end of standard input

Code:
```1 10
100 200
201 210
900 1000```
If that's the input from standard input, how do we know when to stop reading. Isn't a sentinel value required?

2. That number is a starting value and an ending value the program description says that you must generate all the cycle lengths from i to j inclusively. This problem is neat on the theoretical model where it poses again a state of the haulting problem...briefly stated the haulting problem is: Given some program can you ascertain that it will always hault?" This question was posed by Alan Turing and Alonzo Church when they formalized computation theory Turing used a theoretical FSM known as a Turing machine adn Alonozo Church used lambda calculus Google for the Haulting Problem and you will get more information about this program and others like it.

3. The example algorithm used a sentinel value of 1.......

You don't have to use a sentinel value, you could just keep reading while the stream is good.

If it's for a class, ask the prof.

gg

4. This is just one of samples of programming contest problems, whose solution could be submitted through email. I suppose the input would be from screen input therefore doing below won't work and 1 is the sentinel value for the algorithm, not the sentinel value for the *input*.
Code:
```while (std::cin >> a >> b)
{......}```

5. >> ... below won't work ...
It works fine if you supply an EOF character - cntrl-Z for Dos/Windows, cntrl-D for *nix.
Which means it will work nicely when redirecting input from a file, eg. "prog.exe < input.txt".

gg

6. redirecting input from a file...yeah I forgot about that. So I guess that's what they will do with their automated submission system.
Thnx a bunch