#include <bits/stdc++.h>
using namespace std;
const int N = 5005;
const double eps = 1e-13;
int n, T, t[N], pp[N];
double p[N], ans, d[N][N], pt[N];
int main() {
  scanf("%d %d", &n, &T);
  for (int i = 0, x; i < n; i++) {
    scanf("%d %d", &pp[i], &t[i]);
    p[i] = pp[i] / 100.0;
    pt[i] = pow(1 - p[i], t[i] - 1);
  }
  d[0][0] = 1;
  for (int i = 0; i <= n; i++) {
    if (i) {
      for (int j = 0; j <= T; j++) ans += d[i][j];
    }
    if (i == n) break;
    for (int j = 0; j < T; j++) {
      if (d[i][j] < eps) continue;
      double term = d[i][j] * p[i];
      for (int k = 1; k < t[i]; k++) {
        if (term < eps || j + k > T) break;
        d[i + 1][j + k] += term;
        term *= 1.0 - p[i];
      }
      if (j + t[i] <= T) {
        d[i + 1][j + t[i]] += d[i][j] * pt[i];
      }
    }
  }
  printf("%.7f\n", ans);
  return 0;
}
