var primes = (^Inf -> lazy.grep{.is_prime})

var upto = 1e6
var conspiracy = Hash()

primes.first(upto+1).reduce { |a,b|
    var d = b%10
    conspiracy{"#{a} → #{d}"} := 0 ++
    d
}

for k,v in (conspiracy.sort_by{|k,_v| k }) {
    printf("%s count: %6s\tfrequency: %2.2f %\n", k, v.commify, v / upto * 100)
}