using System;
using System.Runtime.Remoting.Contexts;

namespace Contest
{

    class Scanner
    {
        private string[] line = new string[0];
        private int index = 0;
        public string Next()
        {
            if (line.Length <= index)
            {
                line = Console.ReadLine().Split(' ');
                index = 0;
            }
            var res = line[index];
            index++;
            return res;
        }
        public int NextInt()
        {
            return int.Parse(Next());
        }
        public long NextLong()
        {
            return long.Parse(Next());
        }
        public string[] Array()
        {
            line = Console.ReadLine().Split(' ');
            index = line.Length;
            return line;
        }
        public int[] IntArray()
        {
            var array = Array();
            var result = new int[array.Length];
            for (int i = 0; i < array.Length; i++)
            {
                result[i] = int.Parse(array[i]);
            }

            return result;
        }
        public long[] LongArray()
        {
            var array = Array();
            var result = new long[array.Length];
            for (int i = 0; i < array.Length; i++)
            {
                result[i] = long.Parse(array[i]);
            }

            return result;
        }
    }

    class Program
    {
        private int D, G;
        private int[] p, c;
        private void Scan()
        {
            Scanner sc = new Scanner();
            D = sc.NextInt();
            G = sc.NextInt();
            p = new int[D];
            c = new int[D];
            for (int i = 0; i < D; i++)
            {
                p[i] = sc.NextInt();
                c[i] = sc.NextInt();
            }
        }


        public void Solve()
        {
            Scan();
            int loop = 1;
            for (int i = 0; i < D; i++)
            {
                loop *= 3;
            }

            int ans = int.MaxValue;
            for (int i = 0; i < loop; i++)
            {
                int cp = i;
                int cnt = 0;
                int score = 0;
                for (int j = D; j >= 1; j--)
                {
                    int sol = cp % 3;
                    if (sol == 0)
                    {
                        int max = (j * 100) * (p[j - 1] - 1);
                        if (G - score <= max)
                        {
                            int plus = (G - score + (j * 100) - 1) / (j * 100);
                            cnt += plus;
                            score += (j * 100) * plus;
                            break;
                        }
                        else
                        {
                            cnt += p[j - 1] - 1;
                            score += max;
                            if (score >= G)
                            {
                                break;
                            }
                        }
                    }
                    else if (sol == 1)
                    {
                        cnt += p[j - 1];
                        score += (j * 100) * p[j - 1] + c[j - 1];
                        if (score >= G)
                        {
                            break;
                        }
                    }
                    //Console.WriteLine($"{i} {score} {cnt}");

                    cp /= 3;
                }

                if (score >= G)
                {
                    //Console.WriteLine($"{i} {score} {cnt}");
                    ans = Math.Min(ans, cnt);
                }
            }
            Console.WriteLine(ans);
        }

        static void Main() => new Program().Solve();
    }
}

Measured memory_bytes: 13140