#include <bits/stdc++.h>
using namespace std;
int read() {
  int f = 1, x = 0;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * f;
}
int n, m;
double ans, p1;
double d[5005][5005];
double x[5005], t[5005];
int y[5005];
int main() {
  n = read();
  m = read();
  for (int i = 1; i <= n; i++) x[i] = read() / 100.0, y[i] = read();
  d[1][0] = 1;
  x[n + 1] = 0;
  y[n + 1] = 5000;
  for (int i = 1; i <= n + 1; i++) {
    p1 = pow(1 - x[i], y[i]);
    for (int j = 0; j <= m; j++) t[j] = d[i][j];
    for (int j = 0; j <= m; j++) {
      d[i][j + 1] += d[i][j] * (1 - x[i]);
      d[i + 1][j + 1] += d[i][j] * x[i];
      if (j + y[i] <= m) {
        d[i][j + y[i]] -= t[j] * p1;
        d[i + 1][j + y[i]] += t[j] * p1;
      }
    }
  }
  for (int i = 1; i <= n + 1; i++) ans += d[i][m] * (i - 1);
  printf("%.10lf", ans);
}
