#include <bits/stdc++.h>
using namespace std;
int n, kk = 0, k;
char s[11100];
int main()
{
    cin >> n;
    for (int i = (1 << n) - 1; i < (1 << (n + 1)); i++)
    {
        cin >> s[i];
        if (s[i] == '0')
            s[i] = 'B';
        else
            s[i] = 'I';
    }
    while (n--)
    {
        kk = 0;
        for (int i = (1 << n) - 1; i < (1 << (n + 1)); i = i + 2)
        {
            kk++;
            k = (1 << (n - 1)) + k;
            if (s[i] == s[i + 1] && s[i] != 'F')
                s[k] = s[i];
            else
                s[k] = 'F';
        }
    }
    for (int i = 0; i <(1 << (n + 1)); i++)
    {
            cout << s[i];
    }
    return 0;
}