n, x = read_line.split.map &.to_i
ab = (1..2).map { read_line.split.map &.to_i }.transpose.map { |(a, b)| {a - x, b} }
goal = -ab.sum(&.[0])
if goal <= 0
  puts 0
elsif ab.none? { |a, b| a >= 0 }
  puts -1
else
  dp = [0] + [10**9] * (500 * 100)
  ab.select { |a, b| a < 0 }.each { |a, b|
    (0...dp.size + a).reverse_each { |i|
      dp[i - a] = {dp[i - a], dp[i] + b}.min
    }
  }
  puts dp[goal..].min
end