#include <bits/stdc++.h>
using namespace std;
int n, m;
double dp[5000 + 5][5000 + 5];
double p[5000 + 5];
int t[5000 + 5];
double tmp[5000 + 5];
int main() {
  scanf("%d %d", &n, &m);
  for (int i = 1; i <= n; i++) {
    scanf("%lf", &p[i]);
    p[i] /= 100;
    scanf("%d", &t[i]);
  }
  p[n + 1] = 0;
  t[n + 1] = 0x3f3f3f3f;
  dp[1][0] = 1;
  for (int i = 1; i <= n + 1; i++) {
    double p1 = pow(1 - p[i], t[i]);
    for (int j = 0; j <= m; j++) tmp[j] = dp[i][j];
    for (int j = 0; j <= m; j++) {
      dp[i][j + 1] += dp[i][j] * (1 - p[i]);
      dp[i + 1][j + 1] += dp[i][j] * p[i];
      if (j + t[i] <= m) {
        dp[i + 1][j + t[i]] += tmp[j] * p1;
        dp[i][j + t[i]] -= tmp[j] * p1;
      }
    }
  }
  double ans = 0;
  for (int i = 1; i <= n + 1; i++) {
    ans += dp[i][m] * (i - 1);
  }
  printf("%.7f\n", ans);
}
