// #includes {{{
#include <bits/stdc++.h>
using namespace std;
// }}}
// pre-written code {{{
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define RREP(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define FOR(i,c) for(__typeof((c).begin()) i=(c).begin();i!=(c).end();++i)
#define LET(x,a) __typeof(a) x(a)
//#define IFOR(i,it,c) for(__typeof((c).begin())it=(c).begin();it!=(c).end();++it,++i)
#define ALL(c) (c).begin(), (c).end()
#define MP make_pair

#define EXIST(e,s) ((s).find(e)!=(s).end())

#define RESET(a) memset((a),0,sizeof(a))
#define SET(a) memset((a),-1,sizeof(a))
#define PB push_back
#define DEC(it,command) __typeof(command) it=command

//debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#define debug2(x) cerr << #x << " = [";REP(__ind,(x).size()){cerr << (x)[__ind] << ", ";}cerr << "] (L" << __LINE__ << ")" << endl;

const int INF=0x3f3f3f3f;

typedef long long Int;
typedef unsigned long long uInt;
typedef long double rn;

typedef pair<int,int> pii;

/*
#ifdef MYDEBUG
#include"debug.h"
#include"print.h"
#endif
*/
// }}}

const int mod = 1000000007;

//{{{ gcd and inverse
#define __GCD_H
Int gcd(Int a, Int b) {
	return b != 0 ? gcd(b, a % b) : a;
}
Int lcm(Int a, Int b) {
	return a / gcd(a, b) *b;
}
// a x + b y = gcd(a, b)
Int extgcd(Int a, Int b, Int &x, Int &y) {
	Int g = a; x = 1; y = 0;
	if (b != 0) g = extgcd(b, a % b, y, x), y -= (a / b) * x;
	return g;
}
/*
Int invMod(Int a, Int m) {
	Int x, y;
	if (extgcd(a, m, x, y) == 1) return (x + m) % m;
	else                         return 0; // unsolvable
}
*/

inline Int invMod(Int a, Int m){
	Int b = m, u = 1, v = 0;
	while (b) {
		Int t = a / b;
		swap(a -= t * b, b);
		swap(u -= t * v, v);
	}
	return (u % m + m) % m;
}
//}}}
//{{{ modular algebra
struct Num{
	int v;
	Num(int n):v(n){}
	Num(){}
	operator int() const {return v;}
	operator long long() const {return v;}
	void operator =(int n){v=n;}

	template<class T>
		inline void operator *=(const T &a) {
			v = (v*(long long)a)%mod;
		}
	template<class T>
		inline Num operator *(const T &a) {
			Num n(*this);n*=a;
			return n;
		}
	template<class T>
		inline void operator+=(const T &a){
			v+=(int)a;
			if(v>=mod)v-=mod;
			//	assert(0<=v and v<mod);
		}
	template<class T>
		inline Num operator+(const T &a){
			Num n(*this);n+=a;
			return n;
		}
	inline Num operator -(){
		if(v==0)return v;
		else return Num(mod-v);
	}
	template<class T>
		inline void operator -=(const T &a){
			v-=a;
			if(v<0)v+=mod;
		}
	template<class T>
		inline Num operator -(const T &a){
			Num n(*this);n-=a;
			return n;
		}
#ifdef __GCD_H
	inline Num inv(){
		return invMod(this->v,mod);
	}
	template<class T>
		inline void operator /=(const T &a){
			(*this)*=invMod((int)a,mod);
		}
	template<class T>
		inline Num operator /(const T &a){
			Num n(*this);n/=a;
			return n;
		}
#endif
};

ostream& operator <<(ostream &os,const Num &n){
	os<<(int)n.v;
	return os;
}

istream& operator >>(istream &is, const Num &n){
	is>>(int)n.v;
	return is;
}
//}}}

//{{{ pow

/* (x^k)%m */
inline Num pow(Num x, int k){
	if(k==0) return 1;
	Num res(pow(x,k/2));
	res*=res;
	if(k%2)res*=x;
	return res;
}
//}}}

int N;
string s;

Num dp[2][5050];//mod, length

int main(){
	cin>>N>>s;
	const int M = s.size();
	memset(dp,0,sizeof(dp));
	dp[0][0] = 1;
	REP(i,N){
		int from = i%2, to = (i+1)%2;
		memset(dp[to],0,sizeof(dp[to]));
		for(int j=0;j<=N;j++){
			//0 or 1
			if(j+1<=N)dp[to][j+1] += dp[from][j]*2;
			//backspace
			dp[to][max(0,j-1)] += dp[from][j];
		}
	}
	cout<<dp[N%2][M]/pow((Num)2,M)<<endl;
	return 0;
}


Measured memory_bytes: 256