Generate Symmetrical String

Given an integer n (with the constraint $$1 \le n \le 100$$), generate a symmetrical alphanumeric string of length n. A symmetrical string (i.e. a palindrome) reads the same forwards and backwards. The generated string should use the sequence of lowercase letters (a to z) cyclically. Specifically, construct the first half of the string by taking the first floor(n/2) characters from the cyclic sequence, and then mirror them. For odd values of n, an extra middle character is inserted which is also chosen from the sequence.

If the input n is not within the valid range, output -1.

inputFormat

The input consists of a single line containing an integer n.

outputFormat

Output the generated symmetrical string according to the rules described above. If n is outside the valid range, output -1.

5

abcba