[tex]\lfloor x\rfloor[/tex] denotes the floor function, which returns the nearest integer to [tex]x[/tex] that is smaller than or equal to [tex]x[/tex]. For example,
[tex]\lfloor1\rfloor=1[/tex]
[tex]\left\lfloor1+\dfrac12\right\rfloor=1[/tex]
So we have
[tex]\left\lfloor\dfrac14\right\rfloor=0[/tex]
and the answer would be 0.