Problem p03421 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
#ifndef ONLINE_JUDGE
#define dbg(x...)                                                              \
  do {                                                                         \
    cout << "\033[32;1m " << #x << " -> ";                                     \
    err(x);                                                                    \
  } while (0)
void err() { cout << "\033[39;0m" << endl; }
template <template <typename...> class T, typename t, typename... A>
void err(T<t> a, A... x) {
  for (auto v : a)
    cout << v << ' ';
  err(x...);
}
template <typename T, typename... A> void err(T a, A... x) {
  cout << a << ' ';
  err(x...);
}
#else
#define dbg(...)
#endif
typedef long long ll;
typedef pair<int, int> pi;
typedef vector<int> vi;
template <class T> using vc = vector<T>;
template <class T> using vvc = vc<vc<T>>;
template <class T> void mkuni(vector<T> &v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
}
template <class T> void print(T x, int suc = 1) {
  cout << x;
  if (suc == 1)
    cout << '\n';
  else
    cout << ' ';
}
template <class T> void print(const vector<T> &v, int suc = 1) {
  for (int i = 0; i < v.size(); i++)
    print(v[i], i == (int)(v.size()) - 1 ? suc : 2);
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, a, b;
  cin >> n >> a >> b;
  deque<int> ans;
  for (int i = 1; i <= a; i++)
    ans.push_back(i);
  if (b - 1 + a > n)
    print(-1);
  else {
    vi sz(b - 1, 1);
    int tot = b - 1 + a;
    for (int i = 0; i < b - 1; i++) {
      while (sz[i] < a && tot < n) {
        tot++;
        sz[i]++;
      }
    }
    assert(tot == n);
    int p = a + 1;
    for (int i = 0; i < b - 1; i++) {
      vi tmp;
      for (int j = 0; j < sz[i]; j++) {
        tmp.push_back(p);
        p++;
      }
      while (!tmp.empty()) {
        ans.push_front(tmp.back());
        tmp.pop_back();
      }
    }
    vi op;
    while (!ans.empty()) {
      op.push_back(ans.front());
      ans.pop_front();
    }
    print(op);
  }
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#ifndef ONLINE_JUDGE
#define dbg(x...)                                                              \
  do {                                                                         \
    cout << "\033[32;1m " << #x << " -> ";                                     \
    err(x);                                                                    \
  } while (0)
void err() { cout << "\033[39;0m" << endl; }
template <template <typename...> class T, typename t, typename... A>
void err(T<t> a, A... x) {
  for (auto v : a)
    cout << v << ' ';
  err(x...);
}
template <typename T, typename... A> void err(T a, A... x) {
  cout << a << ' ';
  err(x...);
}
#else
#define dbg(...)
#endif
typedef long long ll;
typedef pair<int, int> pi;
typedef vector<int> vi;
template <class T> using vc = vector<T>;
template <class T> using vvc = vc<vc<T>>;
template <class T> void mkuni(vector<T> &v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
}
template <class T> void print(T x, int suc = 1) {
  cout << x;
  if (suc == 1)
    cout << '\n';
  else
    cout << ' ';
}
template <class T> void print(const vector<T> &v, int suc = 1) {
  for (int i = 0; i < v.size(); i++)
    print(v[i], i == (int)(v.size()) - 1 ? suc : 2);
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, a, b;
  cin >> n >> a >> b;
  deque<int> ans;
  for (int i = 1; i <= a; i++)
    ans.push_back(i);
  if (b - 1 + a > n || 1LL * a * b < n)
    print(-1);
  else {
    vi sz(b - 1, 1);
    int tot = b - 1 + a;
    for (int i = 0; i < b - 1; i++) {
      while (sz[i] < a && tot < n) {
        tot++;
        sz[i]++;
      }
    }
    assert(tot == n);
    int p = a + 1;
    for (int i = 0; i < b - 1; i++) {
      vi tmp;
      for (int j = 0; j < sz[i]; j++) {
        tmp.push_back(p);
        p++;
      }
      while (!tmp.empty()) {
        ans.push_front(tmp.back());
        tmp.pop_back();
      }
    }
    vi op;
    while (!ans.empty()) {
      op.push_back(ans.front());
      ans.pop_front();
    }
    print(op);
  }
}