#include <bits/stdc++.h>
using i64 = long long;
#ifdef DEBUG
#include "debug.h"
#else
#define debug(...) void(23)
#endif
template<typename T>
T power(T a, i64 b) {
T res {1};
while (b) {
if (b & 1) {
res *= a;
}
a *= a;
b >>= 1;
}
return res;
}
constexpr int md = int(1E9) + 7;
struct MInt {
int val;
MInt() : val(0) {}
template<typename T>
MInt(T x) {
if (-md <= x && x < md) {
val = x;
} else {
val = x % md;
}
if (val < 0) {
val += md;
}
}
int operator()() { return val; }
MInt& operator+= (MInt rhs) {
if ((val += rhs.val) >= md) {
val -= md;
}
return *this;
}
MInt& operator-= (MInt rhs) {
if ((val -= rhs.val) < 0) {
val += md;
}
return *this;
}
MInt& operator*= (MInt rhs) {
val = int(1LL * val * rhs.val % md);
return *this;
}
MInt inv() {
return power(*this, md - 2);
}
MInt& operator/= (MInt rhs) {
return *this *= rhs.inv();
}
bool operator== (MInt rhs) {
return val == rhs.val;
}
bool operator!= (MInt rhs) {
return val != rhs.val;
}
};
MInt operator+ (MInt lhs, MInt rhs) {
return lhs += rhs;
}
MInt operator- (MInt lhs, MInt rhs) {
return lhs -= rhs;
}
MInt operator* (MInt lhs, MInt rhs) {
return lhs *= rhs;
}
MInt operator/ (MInt lhs, MInt rhs) {
return lhs /= rhs;
}
std::ostream& operator<< (std::ostream& os, MInt x) {
return os << x.val;
}
std::string to_string(MInt x) {
return to_string(x.val);
}
using Z = MInt;
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
int N;
std::cin >> N;
std::vector<int> vis(2 * N);
for (int i = 0; i < N; ++i) {
int X;
std::cin >> X;
--X;
vis[X] = true;
}
std::vector<int> sf(2 * N + 1);
for (int i = 2 * N - 1; i >= 0; --i) {
sf[i] = sf[i + 1] + !vis[i];
}
std::vector<std::vector<Z>> C(N + 1, std::vector<Z>(N + 1));
C[0][0] = 1;
for (int i = 1; i <= N; ++i) {
C[i][0] = 1;
for (int j = 1; j <= i; ++j) {
C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
}
}
std::vector<Z> ways(N + 1);
ways[0] = 1;
for (int i = 1; i <= N; ++i) {
for (int j = 0; j < i; ++j) {
ways[i] += ways[j] * ways[i - 1 - j] * C[i - 1][j] * (i - j + 1);
}
}
std::vector<Z> f(N + 1);
f[0] = 1;
for (int i = 2 * N - 1; i >= 0; --i) {
std::vector<Z> nf(N + 1);
if (vis[i]) {
for (int j = 0; j <= N; ++j) {
if (f[j] == 0) {
continue;
}
nf[j] += f[j];
for (int k = j + 1; k <= N; ++k) {
nf[k] += f[j] * C[(2 * N - 1 - i) - sf[i + 1] - j][k - j - 1] * (k - j + 1) * ways[k - j - 1];
}
}
} else {
for (int j = 0; j <= N; ++j) {
if (f[j] == 0) {
continue;
}
nf[j] += f[j] * (j - sf[i + 1]);
}
}
f = std::move(nf);
// debug(f);
}
Z ans = f[N] / power(Z(2), N);
std::cout << ans << '\n';
return 0;
}
