#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
char c[100000] = { 0 };

int main()
{
    int N, M;
    int step = 1;
    int i, j, k=0, n;
    int flag = 0;
    int sum, t = 0, t1, t2, t3 = 0, t4;
    int Record[1000] = { 0 }, Mid[1000] = { 0 };
    scanf("%d", &N);
    
    if (N > 10 && N != 16) {
        printf("No!!!");
        return 0;
    }
    scanf("%s", c);
    while (step < 30) {
        flag = 0; n = 0;
        t2 = 0, sum = 0;
        t4 = 0; i = 0;
        
            if (step == 1) {
                while ((c[i] != 0)) {
                    if (c[i] <= 57 && c[i] >= 48) {
                        Mid[i] = c[i] - 48;
                    }
                    else {
                        if (c[i] >= 65 && c[i] <= 70) {
                            Mid[i] = c[i] - 55;
                        }
                    }
                    i++;
                }
                n = i;
                for (i = 0; i < n; i++) {
                    t2 += Mid[i] * pow(N, (double)(n - i - 1));
                }
                for (i = 0; i < n; i++) {
                    t4 += Mid[i] * pow(N, (double)(i));
                }
            }
        else {
            for (i = 0; i <= k; i++) {
                t2 += Record[i] * pow(N, (double)(k - i));
            }
            for (i = 0; i <= k; i++) {
                t4 += Record[i] * pow(N, (double)(i));
            }
        }
        t3 = t2 + t4;
        k = 0;
        while (t3) {
            Record[k] = t3 % N;
            t3 /= N;
            k++;
        }
        k--;
        for (i = 0; i <= k; i++) {
            if (Record[i] != Record[k - i]) {
                flag = 1;
                break;
            }
        }
        if (flag == 0) {
            printf("STEP=%d", step);
            break;
        }
        step++;
    }
    if (flag == 1) {
        printf("Impossible!");
    }
}