Adding in SPARQL

Hello,

Could anyone please help me how to add more than one variable (integer) in
SPARQL.


For example:
a=1, 1, 0, 1, 0 ,1
b= 1, 0 ,1, 0,1, 0
c=1, 0, 0, 1, 0 ,1
d= 1, 0 ,0, 0,1, 0

 I tried to do add these 4 variables in SPARQL as follows. But they did not
work.

?R= ?a+?b+?c+?d ................it does not work.
select (sum(?a, ?b, ?c,?d) as ?R) .........it does not work as well.

Could you please tell me how to do this.



Thanks,
Farhana