The task was to reverse file main. This is an executable for MS DOS.
Fortunately, this binary isn't packed and it's logic can be easily understand without dynamic analysis. After few minutes of analysis is becames obvius that this executable set hook for interupt int9 (keyboard handler) and for every input character makes some changes with global variable byte_178. If this variables equals 0x14 then we get success message.
First of all let's take a look at the begging of main function: