#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int n;
string m,d;
string gjdjf(string a,string b)
{
	string d;
	if (a.length() > b.length())
	{
		int c;
		c = a.length() - b.length();
		for (int i = 0; i < c; i++)
		{
			b = "0" + b;
		}
	}
	if (a.length() < b.length())
	{
		int c;
		c = b.length() - a.length();
		for (int i = 0; i < c; i++)
		{
			a = "0" + a;
		}
	}
	int x = 0;
	for (int i = a.length() - 1; i >= 0; i--)
	{
		if (a[i] - '0' + b[i] - '0' + x > n-1)
		{
			d = (char)(a[i] + b[i] - '0' - n + x) + d;
			x = 1;
		}
		else
		{
			d = (char)(a[i] + b[i] - '0' + x) + d;
			x = 0;
		}
	}
	if (x == 1)
	{
		d = '1' + d;
	}
	return d;
}
bool hw(string a)
{
	d = a;
	reverse(a.begin(), a.end());
	return (a == d);
}
int main()
{
	cin >> n>>m;
	for (int i = 0; i < m.length(); i++) {
		if (m[i] >= 'A' && m[i] <= 'Z')m[i] = m[i] - 'A' + 10 + '0';
	}
	for (int i = 1; i <= 31; i++)
	{
		if (i==31)
		{
			cout << "Impossible!";
			break;
		}
		if (hw(m))
		{
			cout << "STEP=" << i;
			break;
		}
		d = m;
		reverse(d.begin(), d.end());
		m = gjdjf(m, d);
	}
	return 0;
}

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