using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static void Main(string[] args)
    {
        new Program().Calc();
    }

    Scanner cin;

    public Program() { }

    int d;
    int g;
    int[] p;
    int[] c;
    int[] sumP;

    int CalcP(int index, int sum, out int remain)
    {
        if (sum < sumP[index])
        {
            if (index * p[index] <= sum)
            {
                remain = 0;
                return p[index];
            }
            else
            {
                int tmpCount = (int)Math.Ceiling(sum / (double)index);
                remain = 0;
                return tmpCount;
            }
        }
        else
        {
            remain = sum - sumP[index];
            return p[index];
        }
    }

    void /*bool[]*/ CalcRec(int remain, int count, bool[] flags, ref int minCount)
    {
        //if (remain <= 0) { return flags; }

        bool[] flags_ = new bool[flags.Length];
        flags.CopyTo(flags_, 0);

        for (int i = d; i >= 1; --i)
        {
            if (!flags_[i])
            {
                int tmpCount = count;
                int outRemain;

                tmpCount += CalcP(i, remain, out outRemain);

                flags_[i] = true;

                if (outRemain == 0)
                {
                    if (minCount > tmpCount)
                    {
                        minCount = tmpCount;
                    }
                    //return flags;
                }
                else
                {
                    /*flags_ =*/ CalcRec(outRemain, tmpCount, flags_, ref minCount);
                }
            }
        }

        return; // flags_;
    }

    void Calc()
    {
        cin = new Scanner();

        d = cin.nextInt();
        g = cin.nextInt() / 100;

        p = new int[d + 1];
        c = new int[d + 1];
        sumP = new int[d + 1];
        //double[] aveP = new double[d];

        for (int i = 1; i <= d; ++i)
        {
            p[i] = cin.nextInt();
            c[i] = cin.nextInt() / 100;

            sumP[i] = i * p[i] + c[i];
            //aveP[i] = (double)sumP[i] / i;
        }

        int minCount = int.MaxValue;

        //for (int i = d; i >= 1; --i)
        {
            bool[] flags = new bool[d + 1];
            //BitArray flags = new BitArray(d + 1);
            //flags[i] = true;

            CalcRec(g, 0, flags, ref minCount);
        }

        Console.WriteLine(minCount);
    }
}

class Scanner
{
    string[] s;
    int i;

    char[] cs = new char[] { ' ' };

    public Scanner()
    {
        s = new string[0];
        i = 0;
    }

    public string next()
    {
        if (i < s.Length) return s[i++];
        string st = Console.ReadLine();
        while (st == "") st = Console.ReadLine();
        s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
        if (s.Length == 0) return next();
        i = 0;
        return s[i++];
    }

    public int nextInt()
    {
        return int.Parse(next());
    }
    public int[] ArrayInt(int N, int add = 0)
    {
        int[] Array = new int[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextInt() + add;
        }
        return Array;
    }

    public long nextLong()
    {
        return long.Parse(next());
    }

    public long[] ArrayLong(int N, long add = 0)
    {
        long[] Array = new long[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextLong() + add;
        }
        return Array;
    }

    public double nextDouble()
    {
        return double.Parse(next());
    }


    public double[] ArrayDouble(int N, double add = 0)
    {
        double[] Array = new double[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextDouble() + add;
        }
        return Array;
    }
}


Measured memory_bytes: 11220