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)

//  cd Desktop/Atcoder
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define rep(i,n) for(i=0;i<(n);i++)
#define ll long long
#define ull unsigned long long
#define MOD 1000000007
#define MYPOW_t ull

MYPOW_t Mypow(MYPOW_t x,MYPOW_t n){
    MYPOW_t ret=1;
    if (n==0) return 1;
    while (n>0) {
        if (n&1) ret=ret*x ;//%MOD;
        x=x*x;//%MOD;
        n>>=1;
    }
    return ret;
}

int main(){
    ll i,j,n,jou=1,cur=0,kake=1,tmp=0,pile=0;
    char ans[300]={};
    scanf("%lld",&n);
    while ((Mypow(26,jou)+pile)<n){
        pile+=Mypow(26,jou);
        jou++;
    }
    for ( i = jou-1; i >=0; i--){
        tmp=Mypow(26,i);
        if(n==0){
            rep(j,300) ans[j]='\0';
            rep(j,jou) ans[j]='z';
        }
        while (tmp*kake<=n) kake++;
        kake--;
        if (kake!=0){
            ans[cur]='a'+kake-1;
            cur++;
        }
        n/=26;
        kake=1;
    }
    printf("%s",ans);
    return 0;
}