GCD Greatest Common Divisor

LCM Least Common Multiple
5,3 = 15
6,12 = 12
8,12 = 24

Demorgan's Law  (Distributing the "not")
Symbol for not "!"
!(T && T || F)
T || T && F

is leap year
if((y % 4 == 0 && y % 100 != 0) || year % 400 == 0){}

is not leap year
if(!((y % 4 == 0 && y % 100 != 0) || year % 400 == 0)){}
if((y % 4 != 0 || y % 100 == 0) && year % 400 != 0){}