#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
const int N = 600 + 5, mod = 1e9 + 7;
int n, h[N][N][2], dp[N][N], pre[N][N], a[N], pa[N], fact[N], inv[N];
inline void add(int &a, int b) {
a = a+b > mod ? a+b-mod : a+b;
}
inline int mul(int a, int b) {
return a*1ll*b%mod;
}
int bp(int a, int p) {
int r = 1;
while(p) {
if(p&1) r = mul(a, r);
a = mul(a, a), p>>=1;
}
return r;
}
void setup() {
for(int i = 0; i < N; i++)
{
if(i < 2) fact[i] = inv[i] = 1;
else fact[i] = i, inv[i] = mod - mul(mod / i, inv[mod % i]);
}
for(int* a : {fact, inv})
{
for(int i = 2; i < N; i++)
{
a[i] = mul(a[i-1], a[i]);
}
}
return;
}
inline int nck(int n, int k) {
return n < 0 || k > n ? 0 : mul(fact[n], mul(inv[n - k], inv[k]));
}
inline int A(int n, int k) {
return n < 0 || k > n ? 0 : mul(fact[n], inv[n - k]);
}
void calch() {
h[0][0][0] = 1;
for(int i = 0; i < n; i++)
{
for(int j = i; j <= n; j++)
{
for(int f = 0; f < 2; f++)
{
add(h[i+1][j][f], mul(h[i][j][f], inv[2]));
add(h[i+1][j+1][f], h[i][j][f]);
add(h[i+1][j+2][f], mul(h[i][j][f], inv[2]));
}
add(h[i+1][j][1], mul(h[i][j][0], inv[2]));
add(h[i+1][j+1][1], mul(h[i][j][0], inv[2]));
}
}
return;
}
inline int prod(int l, int r)
{
if(r < l) return 1;
if(l <= 0) return 0;
return mul(fact[r], inv[l-1]);
}
inline int contrib(int lst, int i)
{
int N = lst - (i>1?pa[i-2]:0);
return prod(N-a[i-1]+1, N);
}
void calcdp()
{
dp[0][0] = 1;
for(int i = 0; i <= n; i++)
{
for(int lst = 0; lst <= i; lst++)
{
int q;
for(int olst = 0; olst < lst; olst++)
{
int dif = lst-olst-1;
q = pre[i][olst];
q = mul(q, mul(h[dif][dif][0] + h[dif][dif][1], A(i-olst-1, dif)));
q = mul(q, contrib(lst, i));
add(dp[i][lst], q);
}
if(i == n || !dp[i][lst]) continue;
q = 1;
for(int ni = i+1; ni <= n; ni++)
{
add(pre[ni][lst], mul(q, dp[i][lst]));
q = mul(q, contrib(lst, ni));
}
}
}
return;
}
int main() {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
setup();
cin >> n;
for(int i = 0; i < n; i++) cin >> a[i];
reverse(a, a + n);
if (a[0] != 2 * n) return cout << 0, 0;
for(int i = 0; i < n; i++) a[i] = a[i] - a[i + 1] - 1;
pa[0] = a[0];
for (int i = 1; i < n; i++) pa[i] = pa[i-1] + a[i];
calch();
calcdp();
cout << dp[n][n];
}
