#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, T;
  cin >> n >> T;
  vector<double> p(n);
  vector<int> t(n);
  for (int i = 0; i < n; i++) {
    cin >> p[i] >> t[i];
    p[i] /= 100;
  }
  cerr << setprecision(5) << fixed;
  vector<double> v(T + 1), w(T + 1);
  for (int i = n - 1; i >= 0; i--) {
    double val = 0;
    double qw = 1;
    for (int ij = 0; ij < t[i] - 1; ij++) qw *= (1 - p[i]);
    for (int j = 0; j <= T; j++) {
      v[j] = val;
      if (j - t[i] >= 0) val -= qw * (w[j - t[i]] + 1);
      val *= (1 - p[i]);
      val += p[i] * (w[j] + 1);
      if (j - t[i] + 1 >= 0) val += qw * (1 - p[i]) * (w[j - t[i] + 1] + 1);
    }
    v.swap(w);
  }
  cout << setprecision(10) << fixed;
  cout << w[T] << "\n";
  return 0;
}
