#include <bits/stdc++.h>
using namespace std;
int D, G;
vector<int> p(D);
vector<int> c(D);
bool dfs(int i, int j, int sum, int d) {
  if (sum >= G) {
    return j;
  }
  if (j < p[i]) {
    if (dfs(i, j + 1, sum + i * 100, d + 1)) {
      return true;
    }
  } else if (j == p[i] && i * 100 * j < p[i] * 100 * i + c[i]) {
    if (dfs(i - 1, 1, p[i] * 100 * i + c[i], d + 1)) {
      return true;
    }
  } else if (j == p[i] && i * 100 * j >= p[i] * 100 + c[i]) {
    if (dfs(i, j + 1, sum + 100 * i, d + 1)) {
      return true;
    }
  }
}
int main() {
  cin >> D >> G;
  for (int i = 0; i < D; i++) {
    cin >> p[i] >> c[i];
  }
  if (dfs(D, 1, 0, 1)) {
    int ans = dfs(D, 1, 0, 1);
    cout << ans << endl;
  }
}
