为什么保龄啊！

#include <bits/stdc++.h>
using namespace std;
int n, step = 0;
int len;
string s1, s2;
inline void work() //计算s2并累加 
{
    for(int i = 0; i < len; i++)
        s2[len-i-1] = s1[i];
    len += 2;
    for(int i = 0; i < len; i++)
    {
        s1[i] = s1[i] + s2[i];
        s1[i+1] += s1[i] / n;
        s1[i] %= n;
    }
    while(!s1[len-1]) len--;
}
inline bool check() //判断是否是回文数 
{
    for(int i = 0; i < len / 2; i++)
        if(s1[i] != s1[len-i-1]) return false;
    else return true;
}
int main()
{
    cin >> n >> s1;
    len = s1.size();
    for(int i = 0; i < len; i++)
    {
        if(s1[i] >= '0' && s1[i] <= '9') s1[i] = s1[i] - '0';
        else s1[i] = s1[i] - 'A' + 10;
    }
    while(check() == false)
    {
        step++;
        if(step > 30) break;
        work();
    }
    if(step <= 30) cout << "STEP=" << step;
    else cout << "Impossible!"; 
    return 0;
}