a,b,c = gets.split.map(&:to_i)
per_week = a*7+b
week = c / per_week
result = week * 7
rest = c - per_week * week
if rest >= a * 7 then
    result += 7
elsif rest % a == 0 then
    result += rest / a
else
    result += rest / a + 1
end
puts result
