Which expression for the YYY placeholder outputs "Quarter century!" when the input is $25,$ and the following C$++$ code is run?

int x;

cin $>>$ x;

if $($ YYY $)\{$

cout $<<$ "Nothing special";

$\}$

else $\{$

cout $<<$ "Quarter century!";

$\}$

x $<>25$

x $==!25$

x $!=25$

x $==25$