Hello Janosandi,
Of course you should set the fuse-bits and config everything at header before anything else. You would add these below lines to your code lines:
Code:
TRISC.1=1 ;Set the C.1 as an input pin
Definitely, a pull-up resistor should be ( you've set this pin as low active!) on C.1
And if you don't mind share your mainloop segment here.