#include <bits/stdc++.h>
using namespace std;
const int MAX = 5123;
const int INF = 0x3f3f3f3f;
const long long MOD = 1000000007;
int n, T;
int s[MAX];
double dp[MAX][MAX];
double p[MAX];
int main() {
  scanf("%d %d", &n, &T);
  for (int i = 1; i <= n; i++) {
    scanf("%lf %d", &p[i], &s[i]);
    p[i] *= .01;
  }
  dp[0][0] = 1;
  double resp = 0;
  for (int i = 1; i <= n; i++) {
    double sum = dp[i - 1][0];
    double fail = 1.0 - p[i];
    for (int j = 1; j <= T; j++) {
      dp[i][j] = sum * p[i];
      sum = sum * (1.0 - p[i]) + dp[i - 1][j];
      if (j < s[i])
        fail *= (1.0 - p[i]);
      else {
        sum -= dp[i - 1][j - s[i]] * fail;
        dp[i][j] += dp[i - 1][j - s[i]] * fail;
      }
      resp += dp[i][j];
    }
  }
  printf("%lf\n", resp);
  return 0;
}
