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 <stdio.h>
#include <math.h>

int main(void)
{
    long long int N, N_copy, N_long, tmp;
    long long int ans;
    int i, l=1;//Nは何文字か
    int j;
    scanf("%lld",&N);
    N_copy = N;
    
    N_long = 0;
    while(N > N_long){
        N_long += pow(26,l);
        l++;
        //printf("N_long = %lld\n",N_long);
    }
    l--;
    printf("l = %d\n",l);
    l--;
    N_copy = N;
    for(i=l; i>0; i--){
        N_long -= pow(26,i+1);
        //printf("N_long = %lld\n",N_long);
        N_copy = N;
        //ans = 0;
        tmp = pow(26,i);
        //
        //printf("tmp = %lld\n",tmp);

        //何回tmpで割って大丈夫かという判断をしながらループする
        j=0;
        //printf("N-j*tmp = %lld\n",N-j*tmp);
        while(N-N_long-j*tmp > 0) {
            //printf("N-j*tmp = %lld\n",N-j*tmp);
            j++;
        }
        //printf("j = %d\n",j);
        /*
        if((N - N_long-26*tmp > 0) && N_copy/tmp > 26){
            ans = 0;
        } else {
            if(N_copy%tmp == 0){
                ans = N_copy/tmp;
                ans--;
                if(i!=1 && N-N_long-ans*tmp < 0) ans--;
            } else {
                ans = N_copy/tmp;
                if(i!=1 && N-N_long-ans*tmp < 0) ans--;
            }
        }
    */

        //printf("ans = %d\n",ans);

        if(j == 0){
            printf("z");
            N -= (26*tmp);
        } else {
            printf("%c",(char)j + 96);
            N -= (j*tmp);
        }
        
        //printf("N_copy = %lld\n",N_copy);


    }
    
    N_copy = N;
    //printf("N_copy = %lld\n",N_copy);
    if(N_copy%26 == 0){
        printf("z\n");
    } else {
        printf("%c\n",(char)N_copy%26 + 96);
    }
    
    return 0;
}