Problem p03421 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
// #pragma GCC optimize("Ofast")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#define ms(s, n) memset(s, n, sizeof(s))
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FORd(i, a, b) for (int i = (a)-1; i >= (b); --i)
#define FORall(it, a)                                                          \
  for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define sz(a) int((a).size())
#define present(t, x) (t.find(x) != t.end())
#define all(a) (a).begin(), (a).end()
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define prec(n) fixed << setprecision(n)
#define bit(n, i) (((n) >> (i)) & 1)
#define bitcount(n) __builtin_popcountll(n)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<int> vi;
typedef vector<pi> vii;
const int MOD = (int)1e9 + 7;
const int FFTMOD = 1007681537;
const int INF = (int)1e9;
const ll LINF = (ll)1e18;
const ld PI = acos((ld)-1);
const ld EPS = 1e-9;
inline ll gcd(ll a, ll b) {
  ll r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
inline ll fpow(ll n, ll k, int p = MOD) {
  ll r = 1;
  for (; k; k >>= 1) {
    if (k & 1)
      r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T> inline int chkmin(T &a, const T &val) {
  return val < a ? a = val, 1 : 0;
}
template <class T> inline int chkmax(T &a, const T &val) {
  return a < val ? a = val, 1 : 0;
}
inline ll isqrt(ll k) {
  ll r = sqrt(k) + 1;
  while (r * r > k)
    r--;
  return r;
}
inline ll icbrt(ll k) {
  ll r = cbrt(k) + 1;
  while (r * r * r > k)
    r--;
  return r;
}
inline void addmod(int &a, int val, int p = MOD) {
  if ((a = (a + val)) >= p)
    a -= p;
}
inline void submod(int &a, int val, int p = MOD) {
  if ((a = (a - val)) < 0)
    a += p;
}
inline int mult(int a, int b, int p = MOD) { return (ll)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(ld x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(ld x, ld y) { return sign(x - y); }
#define db(x) cerr << #x << " = " << (x) << " ";
#define endln cerr << "\n";

void chemthan() {
  int n, a, b;
  cin >> n >> a >> b;
  if (a + b - 1 > n || n > (long long)a * b) {
    cout << -1 << "\n";
    return;
  }
  vector<long long> res;
  FOR(i, 1, a + 1) { res.pb((long long)(b - 1) * a + i); }
  int cnt = n - a;
  FORd(i, b - 1, 0) {
    int num = min(a, cnt - i);
    FOR(j, 1, num + 1) { res.pb((long long)i * a + j); }
  }
  vector<long long> dc = res;
  sort(all(dc));
  FOR(i, 0, n) {
    cout << lower_bound(all(dc), res[i]) - dc.begin() + 1 << " \n"[i == n - 1];
  }
}

int main(int argc, char *argv[]) {
  ios_base::sync_with_stdio(0), cin.tie(0);
  if (argc > 1) {
    assert(freopen(argv[1], "r", stdin));
  }
  if (argc > 2) {
    assert(freopen(argv[2], "wb", stdout));
  }
  chemthan();
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
// #pragma GCC optimize("Ofast")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#define ms(s, n) memset(s, n, sizeof(s))
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FORd(i, a, b) for (int i = (a)-1; i >= (b); --i)
#define FORall(it, a)                                                          \
  for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define sz(a) int((a).size())
#define present(t, x) (t.find(x) != t.end())
#define all(a) (a).begin(), (a).end()
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define prec(n) fixed << setprecision(n)
#define bit(n, i) (((n) >> (i)) & 1)
#define bitcount(n) __builtin_popcountll(n)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<int> vi;
typedef vector<pi> vii;
const int MOD = (int)1e9 + 7;
const int FFTMOD = 1007681537;
const int INF = (int)1e9;
const ll LINF = (ll)1e18;
const ld PI = acos((ld)-1);
const ld EPS = 1e-9;
inline ll gcd(ll a, ll b) {
  ll r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
inline ll fpow(ll n, ll k, int p = MOD) {
  ll r = 1;
  for (; k; k >>= 1) {
    if (k & 1)
      r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T> inline int chkmin(T &a, const T &val) {
  return val < a ? a = val, 1 : 0;
}
template <class T> inline int chkmax(T &a, const T &val) {
  return a < val ? a = val, 1 : 0;
}
inline ll isqrt(ll k) {
  ll r = sqrt(k) + 1;
  while (r * r > k)
    r--;
  return r;
}
inline ll icbrt(ll k) {
  ll r = cbrt(k) + 1;
  while (r * r * r > k)
    r--;
  return r;
}
inline void addmod(int &a, int val, int p = MOD) {
  if ((a = (a + val)) >= p)
    a -= p;
}
inline void submod(int &a, int val, int p = MOD) {
  if ((a = (a - val)) < 0)
    a += p;
}
inline int mult(int a, int b, int p = MOD) { return (ll)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(ld x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(ld x, ld y) { return sign(x - y); }
#define db(x) cerr << #x << " = " << (x) << " ";
#define endln cerr << "\n";

void chemthan() {
  int n, a, b;
  cin >> n >> a >> b;
  if (a + b - 1 > n || n > (long long)a * b) {
    cout << -1 << "\n";
    return;
  }
  vector<long long> res;
  FOR(i, 1, a + 1) { res.pb((long long)(b - 1) * a + i); }
  int cnt = n - a;
  FORd(i, b - 1, 0) {
    int num = min(a, cnt - i);
    cnt -= num;
    FOR(j, 1, num + 1) { res.pb((long long)i * a + j); }
  }
  vector<long long> dc = res;
  sort(all(dc));
  FOR(i, 0, n) {
    cout << lower_bound(all(dc), res[i]) - dc.begin() + 1 << " \n"[i == n - 1];
  }
}

int main(int argc, char *argv[]) {
  ios_base::sync_with_stdio(0), cin.tie(0);
  if (argc > 1) {
    assert(freopen(argv[1], "r", stdin));
  }
  if (argc > 2) {
    assert(freopen(argv[2], "wb", stdout));
  }
  chemthan();
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}