Ok, here are some hints.

Problem #1:

1 - main must return an int, so write int main() instead of just main()
2 - try to give more meaningful names to your variables (i.e. km instead of a,...

no looping at all - just one multiplication needed.
what have you tried?

No it's some sort of pseudo code (like the one I'm used to read in school books - I apologize if it's not a common practice to use it)



I was sure there was a logic explanation, although I was...

something like this should work (warning: untested)

max_sequence := 0
max_sequence_start := 0
for i from 0 to end of file:
current_sequence_start := i
flag = true;
int count :=...

You are kicking off December! :P
Check if(m<=0 || m>=12).
It should be if(m<=0 || m>12).

Also check your leap years handling.