#include<cstdio>
#include<string>
#include<iostream>
#include<algorithm>
using namespace std;

const int maxn = 1005;
int a[maxn],N;

void in(int a[]) {
    string str;
    cin>>N>>str;
    a[0] = str.length();
    for(int i = 1; i <= a[0]; i++) {
        if(str[a[0] - i] >= ‘0‘ && str[a[0] - i] <= ‘9‘) a[i] = str[a[0] - i] - ‘0‘;
        else a[i] = str[a[0] - i] - ‘A‘ + 10;
    }
}

inline bool check(int a[]) {
    for(int i=1; i<=a[0]; i++)
        if(a[i]!=a[a[0]-i+1]) return false;
    return true;
}

inline void Plus(int a[]) {
    int b[maxn];
    for(int i=1; i<=a[0]; i++) b[i]=a[a[0]-i+1];
    for(int i=1; i<=a[0]; i++) a[i]+=b[i];
    for(int i=1; i<=a[0]; i++) {
        a[i+1]+=a[i]/N;
        a[i]%=N;
    }
    while(a[a[0]+1]>0) a[0]++;
    return;
}
int main() {
    in(a);
    if(check(a)) {
        cout<<"STEP=0";
        return 0;
    }
    int ans=0;
    while(ans<=30) {
        ans++;
        Plus(a);
        if(check(a)) {
            cout<<"STEP="<<ans;
            return 0;
        }
    }
    cout<<"Impossible!";
    return 0;
}