Problem p02629 (C++)

Buggy submission (status: Time Limit Exceeded):
#line 2 "codes/header.hpp"

//%snippet.set('header')%
//%snippet.fold()%
#ifndef HEADER_H
#define HEADER_H

// template version 2.0
using namespace std;
#include <bits/stdc++.h>

// varibable settings
const long long INF = 1e18;
template <class T> constexpr T inf = numeric_limits<T>::max() / 2.1;

#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (ll i = (ll)((b)-1); i >= (ll)(a); --i)
#define r_rep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define mt(...) make_tuple(__VA_ARGS__)
#define ub upper_bound
#define lb lower_bound
#define lpos(A, x) (lower_bound(all(A), x) - A.begin())
#define upos(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) {
  if ((a) < (b))
    (a) = (b);
}
template <class T> inline void chmin(T &a, const T &b) {
  if ((a) > (b))
    (a) = (b);
}
template <typename X, typename T> auto make_table(X x, T a) {
  return vector<T>(x, a);
}
template <typename X, typename Y, typename Z, typename... Zs>
auto make_table(X x, Y y, Z z, Zs... zs) {
  auto cont = make_table(y, z, zs...);
  return vector<decltype(cont)>(x, cont);
}

#define cdiv(a, b) (((a) + (b)-1) / (b))
#define is_in(x, a, b) ((a) <= (x) && (x) < (b))
#define uni(x)                                                                 \
  sort(all(x));                                                                \
  x.erase(unique(all(x)), x.end())
#define slice(l, r) substr(l, r - l)

typedef long long ll;
typedef long double ld;
using vl = vector<ll>;
using vvl = vector<vl>;
using pll = pair<ll, ll>;

template <typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
void check_input() {
  assert(cin.eof() == 0);
  int tmp;
  cin >> tmp;
  assert(cin.eof() == 1);
}

#if defined(PCM) || defined(LOCAL)
#else
#define dump(...) ;
#define dump_1d(...) ;
#define dump_2d(...) ;
#define cerrendl ;
#endif

#endif /* HEADER_H */
//%snippet.end()%
#line 2 "codes/solve.cpp"
template <class T = ll> using vec = vector<T>;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

int solve() {
  ll n;
  cin >> n;

  int k = 1;
  int mul = 26;
  ll sum = 26;
  while (sum < n) {
    mul *= 26;
    sum += mul;
    k++;
  }
  dump(k);

  sum -= mul;
  mul /= 26;

  n -= sum;

  string ans(k, '?');

  rep(i, k) {
    char c = 'a';
    while (mul < n) {
      n -= mul;
      c++;
    }
    ans[i] = c;
    mul /= 26;
  }
  cout << ans << endl;

  return 0;
}

int main() { /*{{{*/
  solve();
  check_input();
  return 0;
} /*}}}*/


Fixed submission:
#line 2 "codes/header.hpp"

//%snippet.set('header')%
//%snippet.fold()%
#ifndef HEADER_H
#define HEADER_H

// template version 2.0
using namespace std;
#include <bits/stdc++.h>

// varibable settings
const long long INF = 1e18;
template <class T> constexpr T inf = numeric_limits<T>::max() / 2.1;

#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (ll i = (ll)((b)-1); i >= (ll)(a); --i)
#define r_rep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define mt(...) make_tuple(__VA_ARGS__)
#define ub upper_bound
#define lb lower_bound
#define lpos(A, x) (lower_bound(all(A), x) - A.begin())
#define upos(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) {
  if ((a) < (b))
    (a) = (b);
}
template <class T> inline void chmin(T &a, const T &b) {
  if ((a) > (b))
    (a) = (b);
}
template <typename X, typename T> auto make_table(X x, T a) {
  return vector<T>(x, a);
}
template <typename X, typename Y, typename Z, typename... Zs>
auto make_table(X x, Y y, Z z, Zs... zs) {
  auto cont = make_table(y, z, zs...);
  return vector<decltype(cont)>(x, cont);
}

#define cdiv(a, b) (((a) + (b)-1) / (b))
#define is_in(x, a, b) ((a) <= (x) && (x) < (b))
#define uni(x)                                                                 \
  sort(all(x));                                                                \
  x.erase(unique(all(x)), x.end())
#define slice(l, r) substr(l, r - l)

typedef long long ll;
typedef long double ld;
using vl = vector<ll>;
using vvl = vector<vl>;
using pll = pair<ll, ll>;

template <typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
void check_input() {
  assert(cin.eof() == 0);
  int tmp;
  cin >> tmp;
  assert(cin.eof() == 1);
}

#if defined(PCM) || defined(LOCAL)
#else
#define dump(...) ;
#define dump_1d(...) ;
#define dump_2d(...) ;
#define cerrendl ;
#endif

#endif /* HEADER_H */
//%snippet.end()%
#line 2 "codes/solve.cpp"
template <class T = ll> using vec = vector<T>;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

int solve() {
  ll n;
  cin >> n;

  int k = 1;
  ll mul = 26;
  ll sum = 26;
  while (sum < n) {
    mul *= 26;
    sum += mul;
    k++;
  }
  dump(k);

  sum -= mul;
  mul /= 26;

  n -= sum;

  string ans(k, '?');

  rep(i, k) {
    char c = 'a';
    while (mul < n) {
      n -= mul;
      c++;
    }
    ans[i] = c;
    mul /= 26;
  }
  cout << ans << endl;

  return 0;
}

int main() { /*{{{*/
  solve();
  check_input();
  return 0;
} /*}}}*/