#include <bits/stdc++.h>

using namespace std;
namespace work{
    const int N = 300;
	int a[N], b[N], c[N], c1, c2, c3, n, ans;
string s1;

void add(){
	for(int i = s1.size() - 1; i >= 0; i--){
		if(s1[i] >= '0' && s1[i] <= '9'){
			a[++c1] = s1[i] - '0';
		}else{
			a[++c1] = s1[i] - 'A' + 10;
		}
	}
}

void turn(){
	c2 = 0;
	for(int i = c1; i >= 1; i--){
		b[++c2] = a[i];
	}
}

void plus(){
	c3 = max(c1, c2) + 2;
	memset(c, 0, sizeof c);
	for(int i = 1; i <= c3; i++){
		c[i] += a[i] + b[i];
		c[i + 1] = c[i] / n;
		c[i] %= n;
	}
	while(c[c3] == 0){
		c3--;
	}
}

bool check(){
	for(int i = 1; i <= c3; i++){
		if(c[i] != c[c3 - i + 1]) return 0;
	}
	return 1;
}

void is(){
	c1 = c3;
	for(int i = 1; i <= c3; i++){
		a[i] = c[i]; 
	}
}

void print(){
	cout << "a=";
	for(int i = 1; i <= c1; i++){
		cout << a[i];
	}
	cout << endl;
	cout << "b=";
	for(int i = 1; i <= c2; i++){
		cout << b[i];
	}
	cout << endl;
	cout << "c="; 
	for(int i = 1; i <= c3; i++){
		cout << c[i];
	}
	cout << endl;
}

int main(){
	cin >> n >> s1;
	add();
	turn();
	//print();
	plus();
	//print();
	ans = 1;
	while(!check()){
		is();
		turn();
		plus();
		//print();
		ans++;
	}
	if(ans <= 30){
		cout << "STEP=" << ans << endl;
	}else{
		cout << "Impossible!" << endl;
	}
	return 0;
}
}

int main(){
	work::main();
	return 0;
}

前3个点AC，最后一个RE