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 (Clang 10.0.0) (judge verdict: Accepted)

#include<stdio.h>

long long int calculate(int length)
{
	int i;
	long long int fans=0,ans=1;
	
	for(i=1;i<=length;i++)
	{
		ans*=26;
		fans+=ans;
	}
	
	return fans;
}

int main(void)
{
  long long int number,x;
	int length=1,i;
  char *str;
  
  scanf("%lld",&number);
  
  while(number>calculate(length))
  {
    length++;
  }
  
  str=(char *)malloc(sizeof(char)*length);
  x=number-calculate(length-1)-1;
  
  for(i=0;i<length;i++)
  {
  	str[i]='a'+x%26;
    x/=26;
  }
  
  for(i=length-1;i>=0;i--)
  {
    printf("%c",str[i]);
  }
	
	free(str);
  
  return 0;
}