Need help with piece identification

[langstaff]

Okay I'm trying to figure out what this piece is called and who the composer is.

I don't know what key it is in, but trying playing this:
(Start one octave above middle-C)
C E G B C-D-C - The B there is below the starting C

That's the main melody.

If anyone can identify the tune from that, you're awesome. If more of the melody is required then I'll go to my piano and figure that out.

Gonna blow my brains out if I don't find out what this piece is!

[i heart xenakis]

You're gonna have to be more specific.  Tempo would be helpful, first off.  Also, is the C --> E ascending or descending?

[langstaff]

C     E G = ascending
1 2  3 4

B       C D C      = the B is below the starting C, and the C that follows is the starting C, then go one
1a 2  a  -  3 4      whole tone to D, then back to C. 

I'm not sure what the standard counting format is, but that's how I learned it, with the "a" meaning "and".  The "a -" for C and D are eigth notes.

I'm not 100% sure on the note values, but I think they're right.

The piece is played at a brisk tempo, probably Allegro. 

Let me know if more specifics are needed.

[quantum]

Mozart Sonata K 545, 1st movement

[langstaff]

Yes that's the one!

Thanks