There should be no output, because it shouldn't even compile.
Or, I suppose the output should be something along the lines of
Error: iostream.h: no such file or directory
Then, after you fix that...
In function 'void Secret(char*)':
error: 'L' was not declared in this scope
for (int C=0;C<L/2;C++)
^
At global scope:
error: '::main' must return 'int'
void main()
^
you should probably do some research ldm. there is an iostream.h, but it is outdated and replaced with iostream. @suma: you should probably update your compiler. void main is now considered bad c++. (in fact i think it always was because the standard said main should return an int)