#include <bits/stdc++.h>
using namespace std;
int dx[] = {0, 0, 1, -1, 1, -1, 1, -1};
int dy[] = {1, -1, 0, 0, -1, 1, 1, -1};
long long gcd(long long a, long long b) { return !b ? a : gcd(b, a % b); }
long long lcm(long long a, long long b) { return (a / gcd(a, b)) * b; }
void PLAY() {
  cout << fixed << setprecision(10);
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
int n, l, k;
int p[202], a[202];
double dp[205][205][405];
double solve(int i, int t_cnt, int w) {
  if (i == n) {
    if (t_cnt >= l) return w >= 200;
    return 0;
  }
  double &ret = dp[i][t_cnt][w];
  if (ret == ret) return ret;
  ret = 0;
  double w_p = p[i] / 100.0;
  double l_p = 1 - w_p;
  ret = w_p * solve(i + 1, t_cnt + 1, min(w + a[i], 400));
  ret += l_p * solve(i + 1, t_cnt, w);
  return ret;
}
int main() {
  PLAY();
  memset(dp, -1, sizeof dp);
  cin >> n >> l >> k;
  for (int i = 0; i < n; i++) cin >> p[i];
  for (int i = 0; i < n; i++) cin >> a[i];
  cout << solve(0, 0, 200 + k) << endl;
  return 0;
}
