#include <iostream>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#include <cstdlib>	// require abs exit atof atoi 
#include <cstdio>		// require scanf printf
#include <functional>
#include <numeric>	// require accumulate
#include <cmath>		// require fabs
#include <climits>
#include <limits>
#include <cfloat>
#include <iomanip>	// require setw
#include <sstream>	// require stringstream 
#include <cstring>	// require memset
#include <cctype>		// require tolower, toupper
#include <fstream>	// require freopen
#include <ctime>		// require srand
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()

using namespace std;

typedef long long ll;
typedef pair<int, int> P;

int main()
{
	ios_base::sync_with_stdio(0);
	int N; cin >> N;
	string s = ""; char c; rep (i, N ) cin >> c, s += c;
	string t = ""; char d; rep (i, N ) cin >> d, t += d;
	
	sort (ALL(s ) );
	sort (ALL(t ) );

	int win = 0, sum = 0;
	do{
		do{
			int cnt = 0;
			rep (i, N ){
				if (s[i] > t[i] ) cnt++;
			} // end rep
			win += (cnt > N/2 );
			sum++;	
		}while (next_permutation (ALL(t ) ) );
	}while (next_permutation (ALL (s ) ) );

//	cerr << "win: " << win << endl;
	double res = (double)win/(double)sum;
	printf ("%.4lf\n", res );

	return 0;
}