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When number $\overline{OK}$ is divided by $K$, the result will give the same quotient as the divisor and leave the remainder of $O$. The same letter represents the same digit, and different letters represent different digits. Then, what is the product of the two digits, $O$ and $K$? 
Overseas Competition->Knowledge Point->Combinatorics->Number Puzzles
$89\div9=9R8$ 