#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:250000000")
using namespace std;
int a[1009][1009], b[1009], res;
class actor {
 public:
  int left, right, kol, num;
  bool operator<(actor another) { return right < another.right; }
};
class song {
 public:
  int left, right, new_num_actor, num;
  bool operator<(song another) { return left < another.left; }
};
int n = 0, T;
double p[5009];
int tm[5009];
double P_plus[5009][5009];
void dinam(int k, int t) {
  if (t == 0) {
    P_plus[0][0] = 1;
    dinam(k, t + 1);
    return;
  }
  if (k == n + 1 || (k > 0 && P_plus[k - 1][t] < 1e-9)) {
    dinam(0, t + 1);
    return;
  }
  P_plus[k][t] = P_plus[k][t - 1];
  if (k > 0) {
    P_plus[k][t] += (P_plus[k - 1][t - 1] - P_plus[k][t - 1]) * p[k - 1];
    if (t >= tm[k - 1]) {
      double per = P_plus[k - 1][t - tm[k - 1]];
      if (t > tm[k - 1])
        per = P_plus[k - 1][t - tm[k - 1]] - P_plus[k - 1][t - tm[k - 1] - 1];
      P_plus[k][t] += per * pow(1 - p[k - 1], tm[k - 1]);
    }
  }
  if (t > T + 1) return;
  dinam(k + 1, t);
  return;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n >> T;
  for (int i = 0; i < n; ++i) {
    cin >> p[i] >> tm[i];
    p[i] = p[i] / 100.;
  }
  dinam(0, 0);
  double res = 0;
  for (int i = 1; i <= n; i++) {
    res += P_plus[i][T];
  }
  cout.precision(20);
  cout << res << endl;
  return 0;
}
