#include <bits/stdc++.h>
using namespace std;

int main(){
  long long N;
  cin >> N; // 1 <= N <= 1+10^15 1000000000000001
  string abc = "abcdefghijklmnopqrstuvwxyz";
  string name = "";
  for(int i = 0; i < 11; i++){
    name = abc[(N-1)%26]+name;
    N = (N-1)/26;
    if(N == 0) break;
  }
  cout << name << endl;
}

#include <stdio.h>

#define LL long long
#define ULL unsigned long long
#define UI unsigned int
#define UC unsigned char
#define UL unsigned long

int main() {
	LL llMax = 1000000000000001, llN;
	scanf("%lld", &llN);
	//a = 97
	int iChar[20], iCnt = 0;
	llN--;
	while (iCnt < 20) {
		iChar[iCnt++] = llN % 26;
		if (llN < 26)
			break;
		llN -= (iChar[iCnt - 1] + 1);
		llN /= 26;
		//printf("%lld\n", llN);
	}
	while (iCnt-- > 0) {
		printf("%c", (char)(iChar[iCnt] + 97));
	}

	return 0;
}
