Aha! Did you type make mario.c ?
Because if so, you must not add the .c it's:
./mario 5 (as a height)
Be also sure that you're in the right directory (not in (~):
To know where you are, type in the prompt pwd and it will display you where you are.
If it's the second option, move your mario.c to the right folder, as per the specifications in pset1