#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); i++)
using namespace std;
using ll = long long;
using P = pair<int,int>;

int main(){
	int n;
	cin>>n;

	int k=(1<<n)-1;
	cout<<k<<endl;
	for(int i=1; i<=k; i++){
		string s="";
		rep(i, (1<<n)) s+='A';

		for(int j=0; j<n; j++) if(i>>j&1){
			rep(l, (1<<n)) if(l>>j&1) s[l]=1-(s[l]-'A')+'A';
		}
		cout<<s<<endl;
	}

	return 0;
}

#include<iostream>
#include<string.h>
#include<string>
#include<stdio.h>
#include<algorithm>
#include<vector>
#include<bitset>
#include<math.h>
#include<stack>
#include<queue>
#include<set>
#include<map>
using namespace std;
typedef long long ll;
typedef long double db;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef pair<int,int> pii;
const int N=100000+100;
const db pi=acos(-1.0);
#define lowbit(x) ((x)&(-x))
#define sqr(x) (x)*(x)
#define rep(i,a,b) for (register int i=a;i<=b;i++)
#define per(i,a,b) for (register int i=a;i>=b;i--)
#define go(u,i) for (register int i=head[u],v=sq[i].to;i;i=sq[i].nxt,v=sq[i].to)
#define fir first
#define sec second
#define mkp make_pair
#define pb push_back
#define maxd 1000000007
#define eps 1e-8
inline int read()
{
    int x=0,f=1;char ch=getchar();
    while ((ch<'0') || (ch>'9')) {if (ch=='-') f=-1;ch=getchar();}
    while ((ch>='0') && (ch<='9')) {x=x*10+(ch-'0');ch=getchar();}
    return x*f;
}

inline ll readll()
{
    ll x=0;int f=1;char ch=getchar();
    while ((ch<'0') || (ch>'9')) {if (ch=='-') f=-1;ch=getchar();}
    while ((ch>='0') && (ch<='9')) {x=x*10+(ch-'0');ch=getchar();}
    return x*f;
}

namespace My_Math{
    #define N 100000

    int fac[N+100],invfac[N+100];

    int add(int x,int y) {return x+y>=maxd?x+y-maxd:x+y;}
    int dec(int x,int y) {return x<y?x-y+maxd:x-y;}
    int mul(int x,int y) {return 1ll*x*y%maxd;}
    ll qpow(ll x,int y)
    {
        ll ans=1;
        while (y)
        {
            if (y&1) ans=mul(ans,x);
            x=mul(x,x);y>>=1;
        }
        return ans;
    }
    int getinv(int x) {return qpow(x,maxd-2);}

    int C(int n,int m)
    {
        if ((n<m) || (n<0) || (m<0)) return 0;
        return mul(mul(fac[n],invfac[m]),invfac[n-m]);
    }

    void math_init()
    {
        fac[0]=invfac[0]=1;
        rep(i,1,N) fac[i]=mul(fac[i-1],i);
        invfac[N]=getinv(fac[N]);
        per(i,N-1,1) invfac[i]=mul(invfac[i+1],i+1);
    }
    #undef N
}
using namespace My_Math;

int n,a[N],f[N][2],g[N][2];

int main()
{
    n=read();
    rep(i,1,n) a[i]=read();
    f[1][0]=1;g[1][0]=a[1];
    rep(i,2,n)
    {
        f[i][0]=add(f[i-1][0],f[i-1][1]);
        f[i][1]=f[i-1][0];
        g[i][0]=add(add(g[i-1][0],g[i-1][1]),mul(f[i][0],a[i]));
        g[i][1]=add(g[i-1][0],mul(f[i][1],maxd-a[i]));
    }
    //rep(i,1,n) cout << f[i][0] << " " << f[i][1] << endl;
    printf("%d\n",add(g[n][0],g[n][1]));
    return 0;
}