I might have missed something here, but I think your explanation for the second "instruction" isn't exactly valid. # now B knows-- cut dup days You're not rem

I might have missed something here, but I think your explanation for the second "instruction" isn't exactly valid. # now B knows-- cut dup days You're not removing duplicate days. You're removing months that contained "days occurring once". Because A knows: B doesn't know. Which means A knows it's not on May and June -the only months containing "days occurring once. I solved it this way (in my head). #MONTH doesn't know and knows DAY doesn't know Remove "all days occurring once" Remove "months that contained single occurrence days" #DAY didn't know, but knows now. Remove "duplicate days" #MONTH knows now. Remove "Months with more than 1 day" Leaving July 16. :-)