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<bits/stdc++.h>
#define pi acos(-1)
#define ll long long
#define pii pair<ll,ll>
#define debug(a) cout<<a<<'\n'
#define maxn 200009 /// I wanna be the wind
#define MOD 1000000007
#define F first
#define S second
#define rep(i, a, b) for(ll i = a; i < (b); ++i)
#define per(i, b, a) for(ll i = b-1; i>=a ; i--)
#define trav(a, x) for(auto& a : x)
#define allin(a , x) for(auto a : x)
#define all(x) begin(x), end(x)
#define sz(x) (ll)(x).size()
using namespace std;
const ll INF = 1e17 + 9;
ll fastpow(ll a, ll b){
    ll calc=1;
    for(;b>=1LL;b/=2LL){
        if((b&1LL))calc= calc*a;
        a=a*a;
    }
    return calc;
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll n;
    cin>>n;
    ll qtdl=1;
    ll nreal=n;
    ll fact=26;
    while(nreal>=fact)nreal-=fact,qtdl++,fact*=26;
    rep(i,0,qtdl){
        ll calc = nreal/fastpow(26,qtdl-1-i);
        // cout<<calc<<"\n";
        cout<<char('a' + (calc-(i==qtdl-1)));
        nreal-= calc*fastpow(26,qtdl-1-i);
    }
    cout<<"\n";
    return 0;  
}