#include<iostream>
#include<algorithm>
#include<math.h>
using namespace std;
long long int N, Ma,Mb;
char M1[101];





int main()
{
	cin >> N ;
	cin.ignore();
	cin.getline(M1, 101);






	int step = 0;
	bool isHui = 0;

	for (; !isHui;step++)

	{

		int sizeM = 0;
		for (; M1[sizeM] != '\0'; sizeM++)
		{
		}

		if (step > 30)
		{
			isHui = 0;
			cout << "Impossible!";
			return 0;
		}

		//将N进制的数字转化为十进制以便进行加法
		//Ma就是这个
		Ma = 0;
		for (int i = 0; i <= sizeM; i++)
		{
			if (M1[i] >= '0' && M1[i] <= '9')
			{
				Ma += int(M1[i] - '0') * pow(N, sizeM - i-1);
			}
			if (M1[i] >= 'A' && M1[i] <= 'Z')
			{

				Ma += int(M1[i] - 'A'+10) * pow(N, sizeM - i-1);
			}
			if (M1[i] >= 'a' && M1[i] <= 'z')
			{
				Ma += int(M1[i] - 'a'+10) * pow(N, sizeM - i-1);
			}

		}

		//Mb是这个
		Mb = 0;
		for (int i = 0; i <= sizeM; i++)
		{
			if (M1[i] >= '0' && M1[i] <'A')
			{
				Mb += int(M1[i] - '0') * pow(N, i);
			}
			if (M1[i] >= 'A' && M1[i] <= 'Z')
			{

				Mb += int(M1[i] - 'A'+10) * pow(N, i);
			}
			if (M1[i] >= 'a' && M1[i] <= 'z')
			{
				Mb += int(M1[i] - 'a'+10) * pow(N, i);
			}

		}

		Ma = Ma + Mb;
	//将Ma转化为N进制的M1
		int i = 0;
		for (;Ma!=0 ; i++,Ma/=N)
		{

			char a = char((Ma % N)+'0');

			M1[i] = a;
		}
		M1[i+1]= '\0';
		//判断是否回文
		for (int j = 0; j < i; j++)
		{
			if (M1[j] != M1[i - j - 1])
			{
				isHui = 0;
				break;
			}
			if ((j == i - 1)&&(M1[j]==M1[i-j-1]))
			{
				cout <<"STEP="<< step+1;
				return 0;

			}
		}
	}
	cout << "Impossible!";
	return 0;
}

本地没有毛病，但是为啥在线ide就不可以！！！！！！求指点！