Time limit
1s
Memory limit
1024 MB
1313 factors as 13×101, so it is composite. However, every proper contiguous subnumber of 1313 made from at least two consecutive digits, namely 13, 31, 13, 131, and 313, is prime.
For a positive integer N with at least three digits, define a proper contiguous subnumber as follows. Take two or more consecutive digits from the decimal representation of N, keep their order, and interpret the result as a nonnegative integer. The number N itself is excluded.
A positive integer N is called a composite prime if all three conditions below hold.
A proper contiguous subnumber may start with 0, and the value 0 itself is possible. For example, the proper contiguous subnumbers of 20023 include 20, 00(=0), 02(=2), 23, 200, 002(=2), 023(=23), 2002, and 0023(=23). Since 20 is not prime, 20023 is not a composite prime.
Given a positive integer N, find the largest composite prime not greater than N.
The first line contains the number of test cases T. (1≤T≤105)
Each of the next T lines contains one integer N. (1≤N≤107)
For each test case, print the largest composite prime not greater than N on its own line. If no such number exists, print −1 instead.
Print the answers in the same order as the input test cases.