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#!/usr/bin/env ruby
require 'prime'
def valof(reg_file, reg_or_int)
if reg_or_int >= 'a' && reg_or_int <= 'z' then
return reg_file[reg_or_int] || 0
end
return reg_or_int.to_i
end
input = $stdin.readlines.map(&:chomp)
reg = {'a' => 1}
pc = 0
loop do
break if pc > 7
istr = input[pc].split
case istr[0]
when 'set'
reg[istr[1]] = valof(reg, istr[2])
when 'sub'
reg[istr[1]] = valof(reg, istr[1]) - valof(reg, istr[2])
when 'mul'
reg[istr[1]] = valof(reg, istr[1]) * valof(reg, istr[2])
end
pc += 1
end
n = reg['b']
stop = reg['c']
diff = -input[-2].split.last.to_i
h = 0
# What the horrible program is doing is counting the number of
# composite numbers there are starting with #{b} and incrementing
# by #{diff} until and including #{stop}.
loop do
break if n > stop
h += 1 unless Prime::prime?(n)
n += diff
end
puts h
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