shift left with 1's behind? C language

Question

i would like to know if this is possible...

I know that 255 = 11111111 and if i do 255 << pos*8 with pos=1 i will have 1111111100000000.

I would like to know if is possible to get the value 1111111111111111 with shift left without doing a cicle while or for.

Thanks.

Answer 1

int output = (input << shift) | ((1 << shift) - 1);