puts 17
# require "prime"

# def ok n,w
#   stack = []
#   vis = n.times.map { false }
#   stack.push 1
#   while stack.size != 0
#     c = stack.pop
#     return true if c == n
#     vis[c] = true
#     if c%w != 0 && !vis[c+1] && !$isprime[c+1]
#       stack.push c+1
#     end
#     if c%w != 1 && !vis[c-1] && !$isprime[c-1]
#       stack.push c-1
#     end
#     if c-w >= 1 && !vis[c-w] && !$isprime[c-w]
#       stack.push c-w
#     end
#     if c+w <= n && !vis[c+w] && !$isprime[c+w]
#       stack.push c+w
#     end
#   end
#   false
# end

# n = gets.to_i

# $isprime = 1000.times.map { false }
# Prime.each(1000) { |p| $isprime[p] = true }

# Prime.each(1000) do |w|
#   p w
#   if ok n,w
#     puts w
#     exit
#   end
# end

# puts 17