#include<bits/stdc++.h>
using namespace std;
int n,a[101],b[101],ans,i;
void init(int a[]){
	string s;
	cin>>n>>s;
	memset(a,0,sizeof(a));
	a[0]=s.length();
	for(i=1;i<=a[0];i++)
	if(s[a[0]-i]>='0'&&s[a[0]-i]<='9') a[i]=s[a[0]-i]-'0';
	else a[i]=s[a[0]-i]-'A'+10;
}
bool check(int a[]){
	for(i=1;i<=a[0];i++)
	if(a[i]!=a[a[0]-i+1])return 0;
	return 1;
}
void jia(int a[]){
	int i,k;
	for(i=1;i<=a[0];i++)b[i]=a[a[0]-i+1];
	for(i=1;i<=a[0];i++)a[i]+=b[i];
	for(i=1;i<=a[0];i++){
		a[i+1]+=a[i]/n;
		a[i]%=n;
	}
	if(a[a[0]+1]>0)a[0]++;
}
int main(){
	init(a);
	if(check(a)){
		cout<<0<<endl;
		return 0;
	}
	ans=0;
	while(ans<=30){
		ans++;
		jia(a);
		if(check(a)){
		    cout<<ans<<endl;
		    return 0;
	    }
	}
	cout<<"Impossible";
 	return 0;
}

不是题解，只是当云盘用存一下代码

using namespace std;


int main()
{
	cout << "#include <iostream>" <<endl; 
	cout << "using namespace std;" <<endl;
	cout << "int main(){" << endl;
	cout << "int n;" << endl;
	cout << "cin >>  n;" << endl;
	for (int i=2;i<1000;i++){
		cout << "if(n==" << i << "){" <<endl;
		bool flag =true;
		for (int j=2;j*j<i;j++){
			if (i%j==0){
				flag=false;
			}
		}
		if (flag==false){
			cout <<"    "<< "NO" <<endl;
		}else{
			cout <<"    "<< "YES" <<endl;
		}
	}
	cout << "}";
	
	
 }