When we use a negative construction (with not) in the main clause, until means 'not before'. I won't (will not) start cooking until you come home. until three kilometres.
Medicare Part A is hospital insurance that covers inpatient hospital care and certain home care. Medicare Part A is usually free if you or your spouse paid Medicare taxes while working. If not, it can cost up to $413 each month in 2017. Hospital and skilled nursing facility stays come with deductibles and co-insurance.
Part A is hospital insurance. Most people do not have to pay for Part A. Part B is medical insurance. Most people pay monthly for Part B. Click here for Medicare Premiums for Part A & Part B. (This information is provided by the Center of Medicare & Medicaid Studies.)