Alexandra and Prime Numbers

Alexandra has a little brother. He is new to programming. One day he is solving the following problem: Given an positive integer N, judge whether N is prime.
The problem above is quite easy, so Alexandra gave him a new task: Given a positive integer N, find the minimal positive integer M, such that N/M is prime. If such M doesn't exist, output 0.
Help him!

There are multiple test cases (no more than 1,000). Each case contains only one positive integer N.
$N \leq 1,000,000,000$.
Number of cases with $N > 1,000,000$ is no more than 100.

For each case, output the requested M, or output 0 if no solution exists.

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BestCoder Round #19