#include <bits/stdc++.h>
using namespace std;
const int inf = 1e9, maxn = 5e3 + 23, N = 1e6 + 20, LOG = 21, mod = 1e9 + 7;
const int dx[] = {0, 0, -1, 1}, dy[] = {1, -1, 0, 0};
const long double eps = 1e-13, pi = 3.14159265359;
const pair<unsigned long long, unsigned long long> base = make_pair(1171, 3307);
const long long INF = 1e18;
int n, T, t[maxn];
double dp[maxn][maxn], p[maxn], ans;
int main() {
  cin >> n >> T;
  for (int i = 0; i < n; ++i) {
    cin >> p[i] >> t[i];
    p[i] /= 100;
  }
  dp[0][0] = 1;
  for (int i = 0; i < n; ++i)
    for (int j = 0; j <= T; ++j) {
      if (dp[i][j] < eps) continue;
      long double cur = dp[i][j];
      for (int x = 1; x < t[i] && j + x <= T; ++x) {
        if (cur < eps) break;
        dp[i + 1][j + x] += cur * p[i];
        cur *= (1 - p[i]);
      }
      if (cur >= eps && j + t[i] <= T) dp[i + 1][j + t[i]] += cur;
    }
  for (int i = 1; i <= n; ++i)
    for (int j = 0; j <= T; ++j) ans += dp[i][j];
  cout << setprecision(7) << fixed;
  cout << ans << '\n';
  return 0;
}
