#include<bits/stdc++.h>
using namespace std;
int n,a[30],ans[30],cnt,vis[30],sum;
void dfs(int u){
    if(u==n+1){
        int sk=0;
        for(int i=1;i<=n;i++){
            if(ans[i]|ans[n-i]){
                sum++;
            } 
        } 
        return;
    }
    for(int i=1;i<=n;i++){
        if(!vis[i]){
            ans[++cnt]=a[i];
            vis[i]=1; 
            dfs(u+1);
            vis[i]=0;
            cnt--;           
        } 
    }
} 
int main(){
    freopen("changgao_perm.in","r",stdin);
    freopen("changgao_perm.out","w",stdout);    
    srand(time(0));
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    dfs(1);
    cout<<(rand()%520114)/sum;
    return 0;
}