For $3$ input $OR$ logic $($OR$3),$ if $A=1,$ or $B=1,$ or $C=1,$ or more than two of them are $1,$ the output will be $1.$ Base on that definition, the equation is $OR3=A+B+C,$ the truth table

for OR$3$ is:

ABC OR$3$

$000$ type your answer...

$001$ type your answer...

$010$ type your answer...

$011$ type your answer...

$100$ type your answer...

$101$ type your answer...

$1101$

$1111$