/* In the name of God, aka Allah */
#include<bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define endl '\n'
#define mk make_pair
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int mod = 1e9 + 7;
int add(int a, int b) {
a += b;
if (a >= mod) a -= mod;
if (a < 0) a += mod;
return a;
}
int mul(int a, int b) {
return 1ll*a*b%mod;
}
int pw(int a, int b) {
int out = 1;
while (b) {
if (b&1) out = mul(a, out);
a = mul(a, a);
b >>= 1;
}
return out;
}
const int N = 605;
int n, a[N<<1], dp[N], f[N], C[N][N];
void solve() {
C[0][0] = 1;
for (int x = 1; x < N; x++) {
C[x][0] = 1;
for (int y = 1; y < N; y++) {
C[x][y] = add(C[x-1][y-1], C[x-1][y]);
}
}
cin >> n;
for (int i = 1; i <= n; i++) {
int x;
cin >> x;
a[x] = 1;
}
f[0] = 1;
for (int x = 1; x <= n; x++) {
for (int i = 1; i <= x; i++) {
f[x] = add(f[x], mul(C[x-1][i-1], mul(mul(f[i-1], f[x-i]), x-i+2)));
}
}
dp[0] = 1;
int c0 = 0, c1 = 0;
for (int i = 2*n; i >= 1; i--) {
if (!a[i]) {
for (int x = 0; x <= n; x++) {
if (x <= c0) dp[x] = 0;
else dp[x] = mul(dp[x], x-c0);
}
c0++;
}
else {
for (int x = c1+1; x >= 1; x--) {
for (int y = 0; y < x; y++) {
dp[x] = add(dp[x], mul(dp[y], mul(mul(C[c1-y][x-y-1], f[x-y-1]), x-y+1)));
}
}
c1++;
}
}
cout << mul(dp[n], pw(2, mod-1-n)) << endl;
}
int main() {
ios::sync_with_stdio(0), cin.tie(0);
solve();
return 0;
}
