#include <bits/stdc++.h>
double d[5002][5002];
double x[5002];
double t[5002];
int y[5002];
int main() {
  double r = 0, tt;
  int i, j, n, m;
  scanf("%d%d", &n, &m);
  for (i = 0; i < n; i++) {
    scanf("%lf%d", &x[i], &y[i]);
    x[i] /= 100;
  }
  x[n] = 0;
  y[n] = 10000;
  d[0][0] = 1;
  for (i = 0; i <= n; i++) {
    tt = pow(1 - x[i], y[i]);
    for (j = 0; j <= m; j++) t[j] = d[i][j];
    for (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] * tt;
        d[i + 1][j + y[i]] += t[j] * tt;
      }
    }
  }
  for (i = 0; i < n; i++) r += d[i][m] * i;
  r += d[n][m] * n;
  printf("%.10lf", r);
}
