It is known that when logicians get drunk they may claim not to know the answer to a question when they should know it very well.
After a night of heavy drinking at the bar, three logicians decide that it's time leave. Before they walk out of the place, the barman asks "Is anybody able to drive back home?".
The first logician says "I don't know".
The second logician says "I don't know".
The third logician says "I don't know".
How many logicians must be drunk at a minimum? Provide reasoning.