a1 = 4'b 1001;
a2 = 4'b 1000;
a3 = 4'b 1111;

fulladder fa (a1[3] , a2[3] , a2[4] )

    module full adder (a,b,c, carry , sum);
    body -----
    endmodule

module fulladder2 (a , sum, carry)
 input [2:0] a;
 output sum;
 output carry;
 body-----
endmoduole