题解

实际上是转换26进制，但是要注意0的处理

#include<bits/stdc++.h>
using namespace std;

string f(long long num)
{
    string s="";
    while (num>0)
    {
        if (num%26==0)
        {
            s='Z'+s;
            num=(num-1)/26;
        }
        else
        {
            s=(char)('A'+num%26-1)+s;
            num/=26;
        }
    }
    return s;
}

int main()
{
    long long n;
    cin >> n;
    cout << f(n) << endl;
    return 0;
}