#include <bits/stdc++.h>
using namespace std;
#define GET_MACRO(a, b, c, NAME, ...) NAME
#define rep(...) GET_MACRO(__VA_ARGS__, rep3, rep2)(__VA_ARGS__)
#define rep2(i, a) rep3 (i, 0, a)
#define rep3(i, a, b) for (int i = (a); i < (b); i++)
#define repr(...) GET_MACRO(__VA_ARGS__, repr3, repr2)(__VA_ARGS__)
#define repr2(i, a) repr3 (i, 0, a)
#define repr3(i, a, b) for (int i = (b) - 1; i >= (a); i--)
#define FILL(a, b, T) fill_n((T *)a, sizeof(a) / sizeof(T), b)
template<class T1, class T2> inline bool chmin(T1 &a, T2 b) { return b < a && (a = b, true); }
template<class T1, class T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
using ll = long long;

int main() {
	ll N;
	cin >> N;
	ll num = 1, p = 26;
	while (N >= p) num++, N -= p, p *= 26;
	string ans;
	rep (i, num) {
		ans += N % 26 + 'A';
		N /= 26;
	}
	reverse(ans.begin(), ans.end());
	cout << ans << endl;
	return 0;
}