#include <bits/stdc++.h>
using namespace std;
const int maxn = 5005;
int n, m, t[maxn];
double ans, p1, f[maxn][maxn], p[maxn], tmp[maxn];
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) {
    scanf("%lf%d", p + i, t + i);
    p[i] /= 100.0;
  }
  f[1][0] = 1;
  p[n + 1] = 0;
  t[n + 1] = 5000;
  for (int i = 1; i <= n + 1; ++i) {
    p1 = pow(1 - p[i], t[i]);
    for (int j = 0; j <= m; ++j) tmp[j] = f[i][j];
    for (int j = 0; j <= m; ++j) {
      f[i][j + 1] += f[i][j] * (1 - p[i]);
      f[i + 1][j + 1] += f[i][j] * p[i];
      if (j + t[i] <= m) {
        f[i][j + t[i]] -= tmp[j] * p1;
        f[i + 1][j + t[i]] += tmp[j] * p1;
      }
    }
  }
  for (int i = 1; i <= n + 1; ++i) ans += f[i][m] * (i - 1);
  printf("%.10lf", ans);
}
