This is my first exercise in code obfuscation. This is a legal C program and will compile (tested gcc and pcc) -- I'll let you guess what it does before I tell you (don't cheat by running it).
Code:
_(__,___,____,_____){(__)?printf("%d\n",____),_(__-_____,____,___+____,_____):0;}main(){_(25,0,1,1);}