#include <bits/stdc++.h>
using namespace std;
const double PI = 2.0 * acos(0.0);
const double E = exp(1);
int x[] = {0, 0, -1, 1};
int y[] = {-1, 1, 0, 0};
template <class T1>
void deb(T1 e) {
  cout << e << endl;
}
template <class T1, class T2>
void deb(T1 e1, T2 e2) {
  cout << e1 << " " << e2 << endl;
}
template <class T1, class T2, class T3>
void deb(T1 e1, T2 e2, T3 e3) {
  cout << e1 << " " << e2 << " " << e3 << endl;
}
template <class T1, class T2, class T3, class T4>
void deb(T1 e1, T2 e2, T3 e3, T4 e4) {
  cout << e1 << " " << e2 << " " << e3 << " " << e4 << endl;
}
template <class T1, class T2, class T3, class T4, class T5>
void deb(T1 e1, T2 e2, T3 e3, T4 e4, T5 e5) {
  cout << e1 << " " << e2 << " " << e3 << " " << e4 << " " << e5 << endl;
}
template <class T1, class T2, class T3, class T4, class T5, class T6>
void deb(T1 e1, T2 e2, T3 e3, T4 e4, T5 e5, T6 e6) {
  cout << e1 << " " << e2 << " " << e3 << " " << e4 << " " << e5 << " " << e6
       << endl;
}
template <typename T>
inline T sqr(T n) {
  return n * n;
}
inline double hypot(double x, double y) { return sqrt(sqr(x) + sqr(y)); }
template <typename T>
inline T pmod(T n, T m) {
  return ((n % m) + m) % m;
}
template <typename T>
T power(T n, int p) {
  return (p == 0) ? (T)(1) : (sqr(power(n, p >> 1)) * ((p & 1) * (n - 1) + 1));
}
template <typename T>
T bigmod(T n, int p, T m) {
  return (p == 0)
             ? (T)(1)
             : ((sqr(bigmod(n, p >> 1, m)) % m) * ((p & 1) * (n - 1) % m + 1)) %
                   m;
}
double dp[5005][5005];
double p[5005];
int t[5005];
double pw[5005];
int main() {
  int n, T;
  cin >> n >> T;
  for (int i = 1; i <= n; i++) {
    cin >> p[i] >> t[i];
    p[i] /= 100.00;
    pw[i] = pow(1.00 - p[i], t[i]);
  }
  for (int i = n; i >= 1; i--) {
    for (int j = T; j >= 1; j--) {
      dp[i][j] = p[i] * (dp[i + 1][j + 1] + 1);
      double tmp = dp[i][j + 1] * (1.00 - p[i]);
      if (j + t[i] <= T + 1) tmp += pw[i] * (dp[i + 1][j + t[i]] + 1);
      if (j + t[i] + 1 <= T + 1) tmp -= pw[i] * (dp[i + 1][j + t[i] + 1] + 1);
      dp[i][j] += tmp;
    }
  }
  cout << setprecision(9) << dp[1][1] << "\n";
}
