Problem:
Score : 300 points

Problem Statement

1000000000000001 dogs suddenly appeared under the roof of Roger's house, all of which he decided to keep. The dogs had been numbered 1 through 1000000000000001, but he gave them new names, as follows:

the dogs numbered 1,2,\cdots,26 were respectively given the names a, b, ..., z;

the dogs numbered 27,28,29,\cdots,701,702 were respectively given the names aa, ab, ac, ..., zy, zz;

the dogs numbered 703,704,705,\cdots,18277,18278 were respectively given the names aaa, aab, aac, ..., zzy, zzz;

the dogs numbered 18279,18280,18281,\cdots,475253,475254 were respectively given the names aaaa, aaab, aaac, ..., zzzy, zzzz;

the dogs numbered 475255,475256,\cdots were respectively given the names aaaaa, aaaab, ...;

and so on.

To sum it up, the dogs numbered 1, 2, \cdots were respectively given the following names:

a, b, ..., z, aa, ab, ..., az, ba, bb, ..., bz, ..., za, zb, ..., zz, aaa, aab, ..., aaz, aba, abb, ..., abz, ..., zzz, aaaa, ...

Now, Roger asks you:

"What is the name for the dog numbered N?"

Constraints

N is an integer.

1 \leq N \leq 1000000000000001

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer to Roger's question as a string consisting of lowercase English letters.

Sample Input 1

2

Sample Output 1

b

Sample Input 2

27

Sample Output 2

aa

Sample Input 3

123456789

Sample Output 3

jjddja

Solution in C++ (GCC 9.2.1) (judge verdict: Wrong Answer)

#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<utility>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<functional>
#include<math.h>
using namespace std;
#define N (1000000000+7)
#define M 998244353
#define INF 1e16
typedef long long ll;
typedef pair<int,int> P;
 
ll A(ll x){
    if(x>=0)return x;
    else return -x;
}
 
ll gcd(ll a, ll b) {
	if (b > a) {
		ll tmp = b;
		b = a;
		a = tmp;
	}
	if (a%b == 0)return b;
	else return gcd(b, a%b);
}
 
const double PI=3.14159265358979323846;

const ll X = 1000000000000001;

ll num[100010];

int main(void){
    ll n;
    cin>>n;
    map<int,char>m;
    for(char x='a';x<='z';x++){
        m[((x-'a')+1)%26]=x;
    }
    ll ans = 0;
    ll tmp = 1;
    ll U = 0;
    for(int i=1;i<=12;i++){
        tmp*=26;
        ans = ans+tmp;
        num[i]=ans;
        if(ans>X){
            U = i;
            break;
        }
    }
    ll digit = 0;
    for(int i=1;i<=U;i++){
        if(num[i]>=n){
            digit = i;
        }
    }
    string K ="";
    while(true){
        if(n<26){
            K.push_back(m[n]);
            break;
        }
        else{
            ll r = n%26;
            ll q = n/26;
            digit--;
            if(num[digit]<q){
                q = num[digit];
            }
            K.push_back(m[r]);
            n = q;
        }
    }
    reverse(K.begin(),K.end());
    cout<<K<<endl;
    return 0;
}