#include <bits/stdc++.h>
using namespace std;
using ull=unsigned long long;
const int N=55,mod=1e9+7;
int n,f=1,ans,a[N],p[N];
ull al;
unordered_map<ull,int> mp;
int dfs(int x,ull s,ull b){
	if(x>n) return 1;
	ull t=~s&al;
	if(__builtin_popcountll(t)<=n-x) return 0;
	if(mp.count(b)) return mp[b];
	ull sum=0;
	auto calc=[&](int v){
		if(s>>v&1) return;
		ull nb=b|1llu<<(n-v),ns=s;
		if(v*2>n) ns|=nb<<(v*2-n);
		else ns|=nb>>(n-v*2);
		sum+=dfs(x+1,ns,nb);
	};
	if(!p[x]) for(;t;t-=t&-t) calc(__lg(t&-t));
	else if(t>>p[x]&1) calc(p[x]);
	return mp[b]=sum%mod;
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++) cin>>p[i];
	for(int i=1,cnt=0;i<=n;i++) if(!p[i]) f=1ll*f*++cnt%mod;
	al=(1llu<<(n+1))-2;
	cout<<(f-dfs(1,0,0)+mod)%mod;
	return 0;
}