#include <cstdio>
#include <cstring>
#include <iostream>
int main()
{
	int n;
	char s[100005];
	scanf("%d %s", &n, s);
	int j = 0,ls = strlen(s);
	int sum = 0;
	int a[100005], b[100005];
	for (int i = 1; i <= ls; i++) {
		if (s[i] <= 9 && s[i] >= 0)
			a[i] = s[i] - '0';
		else a[i] = s[i] - 'A';//十六进制
	}
	for (int i = 1; i <= ls; i++) {//倒转
		b[i] = a[ls +1 -i];
	}
	for(int i = 1;i <= ls;i++) {
		if (b == a)
			printf("STEP=%d", sum);
		else {
			b[i] += a[i];
			b[i + 1] += a[i] / n;
			b[i] %= n;
			
			sum++;
		}
		if (b[ls + 1] > 0) 
			ls++;
	}
	printf("Impossible!");
	return 0;
}