module or_1 (y,a,b);
 input a, b;
 output y;

    or x1 (y,a,b);
        
        if ( a == b)
         y = 1'b0;
       else 
         y = 1'bx; 

        if ( a == 0 )
         y = 1'b0;
        else 
         y = 1'b1; 

 
endmodule