#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <cmath>
#include <numeric>
#include <iomanip>
#include <stack>
#include <complex>
#include <functional>
#include <tuple>

using namespace std;

#define Rep(i,a,b) for(ll i = a; i < b; ++i)
#define rep(i,b) Rep(i,0,b)
#define allof(a) (a).begin(), (a).end()

#define Yes(q) ((q) ? "Yes" : "No")
#define YES(q) ((q) ? "YES" : "NO")
#define Possible(q) ((q) ? "Possible" : "Impossible")
#define POSSIBLE(q) ((q) ? "POSSIBLE" : "IMPOSSIBLE")

using ll = long long;

constexpr int inf = 1e9 + 7;
constexpr ll infll = 1ll << 60ll;
constexpr ll mod = 1e9 + 7;
// 0~3までは右左下上 4~7までは斜め
constexpr int dx[] = { 1, 0, -1, 0, 1, 1, -1, -1 };
constexpr int dy[] = { 0, -1, 0, 1, 1, -1, -1, 1 };

namespace {
    template<typename T> bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
    template<typename T> bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

    void Cout(long long x, const char* end = "\n") { std::cout << x << end; }
    template <typename T> void Cout(const T& x, const char* end = "\n") { std::cout << x << end; }
    template <typename T> void Cout(const std::vector<T>& x, const char* sep = " ", const char* end = "\n") { for (std::size_t i = 0, sz = x.size(); i < sz; ++i) { std::cout << x[i] << (i == sz - 1 ? end : sep); } }

    // 標準入出力
    struct inp {
        std::size_t szi, szj;
        inp(std::size_t _szi = 1, std::size_t _szj = 1) : szi(_szi), szj(_szj) {}
        template <typename T> operator T () const { T a; std::cin >> a; return a; }
        template <typename T> operator std::vector<T>() const { std::vector<T> a(szi); for (std::size_t i = 0; i < szi; ++i) std::cin >> a[i]; return a; }
        template <typename T> operator std::vector<std::vector<T>>() const { std::vector<std::vector<T>> a(szi, std::vector<T>(szj));
            for (std::size_t i = 0; i < szi; ++i) for (std::size_t j = 0; j < szj; ++j) cin >> a[i][j]; return a; }
    };
    inp inp1;

    // スコアをG以上にできるか　できる場合は問題数　できない場合はinf
    int rec(int i, int score, int d, int g, vector<bool> used, const vector<int>& p, const vector<int>& c) {
        if (i == d) {
            int prob = 0;
            for (int j = 0; j < used.size(); ++j) if (used[j]) prob += p[j];
            if (score >= g) {
                return prob;
            }
            else {
                // 足りない分を補う
                for (int i = used.size() - 1; i >= 0; --i) {
                    if (!used[i]) {
                        rep(j, p[i] - 1) {
                            if (score >= g) break;
                            score += 100 * (i + 1);
                            ++prob;
                        }
                        break;
                    }
                }
                if (score >= g) return prob;
                else return inf;
            }
        }

        // 使う
        used[i] = true;
        int res = rec(i + 1, score + c[i] + (i + 1) * 100 * p[i], d, g, used, p, c);
        // 使わない
        used[i] = false;
        chmin(res, rec(i + 1, score, d, g, used, p, c));

        return res;
    }
}

int main() {

    int d, g;
    cin >> d >> g;
    vector<int> p(d), c(d);
    rep(i, d) cin >> p[i] >> c[i];

    vector<bool>used(d, false);
    Cout(rec(0, 0, d, g, used, p, c));

    return 0;
}


Measured memory_bytes: 256