#include <bits/stdc++.h>
using namespace std;
constexpr double NIL = -1;
int n;
vector<int> C;
vector<double> P;
vector<vector<vector<double>>> mem;
double dp(int i, int t, int c) {
  if (i == 0) return t <= 0 and c >= 0;
  auto &r = mem[--i][t][c + n];
  if (r == NIL)
    r = P[i] * dp(i, max(0, t - 1), min(n, c + C[i])) +
        (1 - P[i]) * dp(i, t, c);
  return r;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int t, c;
  cin >> n >> t >> c;
  P = vector<double>(n);
  C = vector<int>(n);
  for (auto &p : P) {
    cin >> p;
    p /= 100;
  }
  for (auto &v : C) cin >> v;
  mem = vector<vector<vector<double>>>(
      n, vector<vector<double>>(n + 2, vector<double>(2 * n + 1, NIL)));
  cout << dp(n, min(t, n + 1), min(c, n)) << '\n';
  return 0;
}
