206 Concealed Square.sf

#!/usr/bin/ruby

# Author: Trizen
# Date: 24 August 2016
# Translated: 16 November 2023
# https://github.com/trizen

# https://projecteuler.net/problem=206

# Runtime: 0.263s

var n = isqrt(1020304050607080900)    # lower-limit
var m = isqrt(1929394959697989990)    # upper-limit

for (var i = (m + (10 - (m % 10))) ; i >= n ; i -= 10) {
    if (i.sqr.to_s =~ /^1.2.3.4.5.6.7.8.9.0\z/) {
        say i
        break
    }
}