#include <bits/stdc++.h>
#define rep(i,a,n) for (int i = (a); i < (n); i++)
using namespace std;
typedef long long ll;
typedef pair<int,int> P;

int main(){
  ll n;
  cin >> n;
  string s;
  while(n>0){
    int r = n%26;
    char c;
    if(r>0) c = 'a' + r - 1;
    else c = 'z';
    s += c;
    n /= 26;
    if(r==0) n--;
  }
  reverse(s.begin(),s.end());
  cout << s << endl;
  return 0;
}
#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;
}
