Mystery Phone Number
	"Hello, this is Dave.   We met last night..."

Dave goes to a museum and meets a lovely lady.  Wasting no time, Dave asks the lady for her phone number.  He copies the number down.  But on the walk home, the paper flies from Dave's pocket, blowing the phone number, along with his hopes, into the East River.  Despondent, Dave ponders his situation on the train ride home and manages to remember all seven digits (4,3,7,8,2,6,5) of the woman's phone number.  However, he does not  remember the sequence of the numbers.  Dave is determined to sit in front of the phone all night if necessary to contact this lovely lady.  How many telephone numbers must Dave dial to guarantee that he makes a love connection? 

Solution 3

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