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

#undef _P
#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define RFOR(i,a,b) for (int i = (b)-1; i >= (a); i--)
#define REP(i,n) for (int i = 0; i < (n); i++)
#define RREP(i,n) for (int i = (n)-1; i >= 0; i--)
#define ALL(x) (x).begin(), (x).end()
#define ITR(x,c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define RITR(x,c) for(__typeof(c.rbegin()) x=c.rbegin();x!=c.rend();x++)
#define MP(x,y) make_pair((x), (y))
#define MIN(a,b) (a < b ? a : b)
#define MAX(a,b) (a > b ? a : b)
#define AMIN(a,b) if(b < a) (a) = (b)
#define AMAX(a,b) if(b > a) (a) = (b)
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
#define bitcount(b) __builtin_popcount(b)
#define GCD(a,b) (__gcd(a,b))
#define GCD3(a,b,c) (GCD(GCD(a,b), c))
#define LCM(a,b) (a/GCD(a,b)*b)
#define LCM3(a,b,c) LCM(LCM(a,b),c)
#define MOD 1000000007
typedef long long ll;
// -------------------------------------

int main() {
  long N;
  cin >> N;

  vector<char> ans;
  ans.push_back('A' + N % 26);
  N /= 26;

  while (N) {
    ans.push_back('A' + --N % 26);
    N /= 26;
  }

  cout << string(ans.rbegin(), ans.rend()) << endl;

  return 0;
}