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Jacob writes down a three-digit number on a piece of paper. Lisa, Mike, and Henry are guessing the number Jacob writes down.  Lisa: "The number is $473$."  Mike: "The number is $623$."  Henry: "The number is $428$."  Among the three digits, each person guesses two of them correctly for both digits and their positions.  What is the number Jacob writes down? 
Overseas Competition->Knowledge Point->Combinatorics->Logical Reasoning
In the hundreds place, $4$ appears twice, so $4$ is in the hundreds place.  In the tens place, $2$ appears twice, so $2$ is in the tens place.  In the ones place, $3$ appears twice, so $3$ is in the ones place.  Thus, the number Jacob writes down is $423$. 