There are six balls numbered with $$1-6$$. Amy distributes them equally among three people and each time she needs the three people give her a digit from the two balls they got, then she will use the three digits to form a three$-$digit number. She does it three times, and the numbers are $$145$$, $$263$$, and $$651$$. Which two numbers below must belong to one person? 
Overseas Competition->Knowledge Point->Combinatorics->Logical Reasoning
According to $145$ and $651$, we can find that only $4$ and $6$ have changed with each other. So, they belong to one person. 