#include <bits/stdc++.h>
using namespace std;
template <typename T1, typename T2>
inline void chkmin(T1 &x, T2 y) {
  if (x > y) x = y;
}
template <typename T1, typename T2>
inline void chkmax(T1 &x, T2 y) {
  if (x < y) x = y;
}
inline int readChar();
template <class T = int>
inline T readInt();
template <class T>
inline void writeInt(T x, char end = 0);
inline void writeChar(int x);
inline void writeWord(const char *s);
static const int buf_size = 4096;
inline int getChar() {
  static char buf[buf_size];
  static int len = 0, pos = 0;
  if (pos == len) pos = 0, len = fread(buf, 1, buf_size, stdin);
  if (pos == len) return -1;
  return buf[pos++];
}
inline int readChar() {
  int c = getChar();
  while (c <= 32) c = getChar();
  return c;
}
template <class T>
inline T readInt() {
  int s = 1, c = readChar();
  T x = 0;
  if (c == '-') s = -1, c = getChar();
  while ('0' <= c && c <= '9') x = x * 10 + c - '0', c = getChar();
  return s == 1 ? x : -x;
}
static int write_pos = 0;
static char write_buf[buf_size];
inline void writeChar(int x) {
  if (write_pos == buf_size)
    fwrite(write_buf, 1, buf_size, stdout), write_pos = 0;
  write_buf[write_pos++] = x;
}
template <class T>
inline void writeInt(T x, char end) {
  if (x < 0) writeChar('-'), x = -x;
  char s[24];
  int n = 0;
  while (x || !n) s[n++] = '0' + x % 10, x /= 10;
  while (n--) writeChar(s[n]);
  if (end) writeChar(end);
}
inline void writeWord(const char *s) {
  while (*s) writeChar(*s++);
}
struct Flusher {
  ~Flusher() {
    if (write_pos) fwrite(write_buf, 1, write_pos, stdout), write_pos = 0;
  }
} flusher;
const int MAXN = 2001;
int n, a, b;
int dp[MAXN][MAXN];
int t[MAXN];
double pp[MAXN], qq[MAXN];
int main() {
  scanf("%d %d %d", &n, &a, &b);
  for (int i = 0; i < n; i++) {
    scanf("%lf", &pp[i]);
  }
  for (int i = 0; i < n; i++) {
    scanf("%lf", &qq[i]);
  }
  for (int i = 0; i < n; i++) {
    int A = pp[i] * 1000000;
    int B = qq[i] * 1000000;
    int C = (pp[i] + qq[i] - pp[i] * qq[i]) * 1000000;
    int k1 = min(i, a);
    int k2 = min(i, b);
    for (int j = k1; j >= 0; j--) {
      for (int k = k2; k >= 0; k--) {
        chkmax(dp[j + 1][k + 1], dp[j][k] + C);
        chkmax(dp[j + 1][k], dp[j][k] + A);
        chkmax(dp[j][k + 1], dp[j][k] + B);
      }
    }
  }
  double ans = double(dp[a][b]) / 1000000;
  printf("%.10lf\n", ans);
  return 0;
}
