#include <bits/stdc++.h>
using namespace std;
struct thanks {
  double pt;
  int vt;
} p[5005];
double dp[5005][5005], sp[5005], vat, dat;
int main() {
  int i, j, n, m, ans = 0, t;
  scanf("%d%d", &n, &t);
  for (i = 1; i <= n; i++) {
    scanf("%lf%d", &p[i].pt, &p[i].vt);
    p[i].pt *= 0.01;
    sp[i] = pow(1.0 - p[i].pt, p[i].vt - 1.0);
  }
  for (i = 1; i <= t; i++) {
    for (j = 1; j <= n; j++) {
      if (i >= p[j].vt) {
        dp[i][j] =
            (dp[i - 1][j] -
             (i >= p[j].vt + 1 ? dp[i - p[j].vt - 1][j + 1] + 1 : 0) * sp[j] +
             (dp[i - p[j].vt][j + 1] + 1) * sp[j]) *
                (1 - p[j].pt) +
            (dp[i - 1][j + 1] + 1) * p[j].pt;
      } else {
        dp[i][j] =
            dp[i - 1][j] * (1 - p[j].pt) + (dp[i - 1][j + 1] + 1) * p[j].pt;
      }
    }
  }
  printf("%.9lf\n", dp[t][1]);
  return 0;
}
