Please remember, that:
1. I recommend you to use the most accurate floating-point type you have (C# = decimal, Pascal = extended etc.)

2. use constant:
s = 0.70710678118654752440084436210485

3. Some tests have no '0' symbol.

4. (For notebook owners) Remember, that the author of the statement said to use computer digit keys (not telephone digit keys!).
So the numbers are situated in such order:

7 8 9
4 5 6
1 2 3

Thank you very much!

Thank you for keyboard!! P.S. I used to write sqrt(2)/2 and got AC. (use pascal)