package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"strconv"
)

func main() {
	sc := NewScanner(os.Stdin)
	N, _ := sc.NextInt()
	sections := make([]section, N)
	for i := 0; i < N; i++ {
		sections[i].limit, _ = sc.NextInt()
		sections[i].typing, _ = sc.Next()
	}

	fmt.Println(solve(sections))
}

func solve(sections []section) (got int, loss int) {
	for _, sct := range sections {
		len := len(sct.typing)
		cnt := 12 * sct.limit / 1000
		if cnt >= len {
			got += len
		} else {
			got += cnt
			loss += len - cnt
		}
	}
	return
}

type section struct {
	limit  int
	typing string
}

type Scanner struct {
	*bufio.Scanner
}

func NewScanner(r io.Reader) *Scanner {
	return &Scanner{
		bufio.NewScanner(r),
	}
}

func (s *Scanner) Next() (string, error) {
	s.Scanner.Split(bufio.ScanWords)
	return s.nextToken()
}

func (s *Scanner) nextToken() (string, error) {
	sc := s.Scanner
	if sc.Scan() {
		return sc.Text(), nil
	}
	if sc.Err() != nil {
		return "", sc.Err()
	}
	return "", io.EOF
}

func (s *Scanner) NextInt() (int, error) {
	token, err := s.Next()
	if err != nil {
		return 0, err
	}
	return strconv.Atoi(token)
}