Walgreen Co said on Monday it will provide a month´s supply of certain prescriptions at no upfront cost to U.S. participants who have not yet received a plan identification number under President Barack Obama´s signature healthcare law. The offering comes as U.S. government officials struggle to roll out the Affordable Care Act, also known as Obamacare. Myriad enrollment problems have dogged the site´s website, HealthCare.gov, since its October launch and many insurance companies have said they are not getting accurate enrollee information to be able to process required forms. Walgreen, the largest drug store chain in the United States, said