#include <bits/stdc++.h>
using namespace std;
int getint() {
  unsigned int c;
  int x = 0;
  while (((c = getchar()) - '0') >= 10) {
    if (c == '-') return -getint();
    if (!~c) exit(0);
  }
  do {
    x = (x << 3) + (x << 1) + (c - '0');
  } while (((c = getchar()) - '0') < 10);
  return x;
}
const int L = 222;
const int G = 222;
int nTour, needWin, initCap;
double winProb[200];
int award[200];
double cache[L][L + G + 1][L];
double solve(int pos, int cap, int won) {
  double& res = cache[pos][cap][won];
  if (res > -1) return res;
  if (pos == nTour) {
    if (won >= needWin) {
      if (cap >= G) {
        return res = 1;
      } else {
        return res = 0;
      }
    } else {
      return res = 0;
    }
  }
  if (award[pos] == -1) {
    res = winProb[pos] * solve(pos + 1, cap - 1, won + 1);
  } else {
    res = winProb[pos] * solve(pos + 1, min(L + G, cap + award[pos]), won + 1);
  }
  res += (1 - winProb[pos]) * solve(pos + 1, cap, won);
  return res;
}
int main() {
  int i, j, k, tcc, tc = 1 << 28;
  for (tcc = 0; tcc < tc; tcc++) {
    nTour = getint();
    needWin = getint();
    initCap = getint();
    for (i = 0; i < nTour; i++) {
      winProb[i] = getint() / 100.0;
    }
    for (i = 0; i < nTour; i++) {
      award[i] = getint();
    }
    for (i = 0; i < L; i++)
      for (j = 0; j < L + G + 1; j++)
        for (k = 0; k < L; k++) cache[i][j][k] = -1e40;
    double res = solve(0, initCap + G, 0);
    printf("%.10lf\n", res);
  }
  return 0;
}
