import java.io._
import java.util.StringTokenizer
import scala.util.control.Breaks.{breakable,break}

object Main extends App {
  val in = new InputReader(System.in)
  val pw = new PrintWriter(System.out)

  val D, G = in.next().toInt
  val p = new Array[Int](D+1)
  val c = new Array[Int](D+1)

  for(i <- 1 to D) {
    val a, b = in.next().toInt
    p(i) = a; c(i) = b / 100
  }


  //
  val MAX = 20000
  val IM = Int.MaxValue
  val dp = Array.fill[Int](MAX+1)(IM)
  dp(0) = 0
  for(k <- 1 to D) {
    val np = p(k); val nc = c(k)

    for(i <- (1 to MAX).reverse) {
      for (j <- 1 until np) {
        val now = i - (k * j)
        if(now >= 0)
          if(dp(now) != IM) {
            dp(i) = dp(i) min (dp(now) + j)
          }
      }

      val clear = i - (k * np) - nc
      if(clear >= 0)
        if(dp(clear) != IM) {
          dp(i) = dp(i) min (dp(clear) + np)
        }
    }
  }

  var ans = IM
  for (i <- G/100 to MAX)
    ans = ans min dp(i)
  println(ans)
}


class InputReader(stream: InputStream) {
  private val reader = new BufferedReader(new InputStreamReader(stream))
  private var tokenizer: StringTokenizer = new StringTokenizer(reader.readLine())
  def next(): String = {
    while (!tokenizer.hasMoreTokens()) {
      tokenizer = new StringTokenizer(reader.readLine())
    }
    tokenizer.nextToken()
  }
}
