#include <algorithm>
#include <climits>
#include <cmath>
#include <deque>
#include <iostream>
#include <map>
#include <memory>
#include <numeric>
#include <set>
#include <string>
#include <utility>
#include <vector>

using namespace std;

class NyaGadgetPositionalNotation
{	// N進数を表現するクラス
public:
	NyaGadgetPositionalNotation(int cardinal)
	{
		cardinal_ = cardinal;
		symbol_index_collection_.push_back(0);
	}
	void Inc()
	{	// 返り値なしのインクリメント
		bool carry = true;
		long index = (long)symbol_index_collection_.size() - 1;
		while (0 <= index && carry)
		{
			if (symbol_index_collection_[index] != cardinal_ - 1)
			{
				symbol_index_collection_[index]++;
				carry = false;
			}
			else
			{	// 桁上り
				symbol_index_collection_[index] = 0;
				if (index == 0)
					symbol_index_collection_.push_front(1);
				carry = true;
			}
			index--;
		}
	}
	NyaGadgetPositionalNotation operator ++()
	{	// 前置インクリメント
		Inc();
		return *this;
	}
	NyaGadgetPositionalNotation operator ++(int)
	{  // 後置インクリメント
		NyaGadgetPositionalNotation pn = *this;
		Inc();
		return pn;
	}
	/**
	@brief N進数取得関数
	@note
	 d桁のN進数として文字列で取得
	---------------------------------------------------------------------------
	[sample]
	int main()
	{	// 16進数テスト
		NyaGadgetPositionalNotation pn(16);

		for (int i = 0; i < 30; i++)
			pn++;

		cout << pn() << endl;		// 30を16進数で表示
		cout << pn(5) << endl;		// 5桁表示

		return 0;
	}
	---------------------------------------------------------------------------
	[output]
	1E
	0001E
	**/
	string operator()(long d = 0)
	{
		std::string positional_nation;

		for (const auto& e : symbol_index_collection_)
			positional_nation += symbols_[e];

		if (d == 0 || d == positional_nation.size())
			return positional_nation;

		if (positional_nation.size() < d)
		{	// 表示桁に空きがあるときは0で埋める
			std::string zero(d - positional_nation.size(), '0');
			positional_nation = zero + positional_nation;
		}

		return positional_nation;
	}
	/**
	@brief d桁目を取得する演算子
	@note
	 d桁目の数字を文字列で取得する。
	-------------------------------------------------------------------------- -
	[sample]
	int main()
	{	// 16進数テスト
		NyaGadgetPositionalNotation pn(16);

		for (int i = 0; i < 30; i++)
			pn++;

		cout << pn.() << endl;		// 30を16進数で表示
		cout << pn[0] << endl;		// １桁目を表示
		cout << pn[1] << endl;		// ２桁目を表示

		return 0;
	}
	-------------------------------------------------------------------------- -
	[output]
	1E
	E
	1
	**/
	char operator[](int d)
	{	// d桁目の数字を取得する
		int index = (int)symbol_index_collection_.size() - 1 - d;
		if (index < 0)
			return symbols_[0][0];
		return symbols_[symbol_index_collection_[index]][0];
	}
private:
	int cardinal_;	// 基数
	string symbols_[36] =
	{	// 36進数まで対応
		"0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
		"A", "B", "C", "D", "E", "F", "G", "H", "I", "J",
		"K", "L", "M", "N", "O", "P", "Q", "R", "S", "T",
		"U", "V", "W", "X", "Y", "Z",
	};
	// シンボルそのものでなく、シンボルに対応するindexを格納していく
	deque<int> symbol_index_collection_;
};


using namespace std;

#define all(collection) (collection).begin(), (collection).end()
#define loop(i, times) for(long i = 0; i < times; i++)
#define rloop(i, times) for(long i = times - 1; 0 <= i; i--)
#define seloop(i, start_index, end_index) for(long i = start_index; i < end_index; i++)
#define eqseloop(i, start_index, end_index) for(long i = start_index; i <= end_index; i++)

struct Problem
{
	long bonus_;	//!< ボーナス点
	int level_;		//!< 問題のレベル(100*X点)
	int n_;			//!< 問題数
	Problem()
	{
		bonus_ = level_ = n_ = 0;
	}
};

struct Solve
{
	long count_;	//!< 解答数 
	long score_;	//!< スコア
	Solve()
	{
		count_ = score_ = 0;
	}
	bool operator < (const Solve& s) const
	{
		return (count_ < s.count_);
	}
};

class Abc104C
{
public:
	void Run(void)
	{
		int d; cin >> d;
		long g; cin >> g;

		problem_collection_.resize(d);
		loop(i, d)
		{	// 問題の入力
			cin >> problem_collection_[i].n_;
			cin >> problem_collection_[i].bonus_;
			problem_collection_[i].level_ = (i + 1) * 100;
		}

		solve_collection_.resize(1LL << d);
		NyaGadgetPositionalNotation pn(2);
		loop(bit_loop_times, 1L << d)
		{	// bit全探索で問題を解く
			loop(i, (long)pn(d).size())
			{
				if (pn[i] == '1')
					SolveAll(problem_collection_[i], solve_collection_[bit_loop_times]);
			}
			rloop(i, (long)pn(d).size())
			{
				if (pn[i] == '0')
					SolveX(problem_collection_[i], solve_collection_[bit_loop_times], g);
			}
			pn++;
		}

		// 解いた問題数の昇順にソート
		sort(solve_collection_.begin(), solve_collection_.end());
		for (const auto & elm_solve : solve_collection_)
		{	// 解いた問題数の出力


			if (g <= elm_solve.score_)
			{
				cout << elm_solve.count_;
				return;
			}
		}
	}
	/**
	@brief 問題をX個解く関数
	@note
	 問題problemを(problem.n_-1)個だけ解いて、解答solveを更新する。
	 ただし、solve.score_がgoalに達したら解くのを中断する。
	**/
	void SolveX(const Problem& problem, Solve& solve, const long goal)
	{
		loop(i, problem.n_ - 1)
		{
			if (goal <= solve.score_)
				return;
			solve.score_ += problem.level_;
			solve.count_++;
		}
	}
	/**
	@brief 問題を全て解く関数
	@note
	 問題problemをボーナスを得るまで解いて、解答solveを更新する。
	**/
	void SolveAll(const Problem& problem, Solve& solve)
	{
		solve.score_ += problem.level_ * problem.n_ + problem.bonus_;
		solve.count_ += problem.n_;
	}

private:
	vector<Problem> problem_collection_;
	vector<Solve> solve_collection_;
};

int main()
{
	Abc104C abc104c;
	abc104c.Run();
	return 0;
}

Measured memory_bytes: 764