Problem p03332 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 998244353
#define EPS 1e-10
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; --i)
#define srep(i, s, t) for (int i = (int)(s); i < (int)(t); ++i)
#define each(a, b) for (auto &(a) : (b))
#define all(v) (v).begin(), (v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)), v.erase(unique(all(v)), v.end())
#define cmx(x, y) x = max(x, y)
#define cmn(x, y) x = min(x, y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout << #x << " = " << (x) << endl
#define sar(a, n)                                                              \
  cout << #a << ":";                                                           \
  rep(pachico, n) cout << " " << a[pachico];                                   \
  cout << endl

using namespace std;

template <typename S, typename T> auto &operator<<(ostream &o, pair<S, T> p) {
  return o << "{" << p.fi << "," << p.se << "}";
}
template <typename T> auto &operator<<(ostream &o, set<T> s) {
  for (auto &e : s)
    o << e << " ";
  return o;
}
template <typename S, typename T, typename U>
auto &operator<<(ostream &o, priority_queue<S, T, U> q) {
  while (!q.empty())
    o << q.top() << " ", q.pop();
  return o;
}
template <typename K, typename T> auto &operator<<(ostream &o, map<K, T> m) {
  for (auto &e : m)
    o << e << " ";
  return o;
}
template <typename T> auto &operator<<(ostream &o, vector<T> v) {
  for (auto &e : v)
    o << e << " ";
  return o;
}
void ashow() { cout << endl; }
template <typename T, typename... A> void ashow(T t, A... a) {
  cout << t << " ";
  ashow(a...);
}

typedef pair<int, int> P;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<P> vp;
typedef vector<double> vd;
typedef vector<string> vs;

const int MAX_N = 100005;

template <uint mod> class ModInt {
private:
  uint v;
  static uint norm(const uint &x) { return x < mod ? x : x - mod; }
  static ModInt make(const uint &x) {
    ModInt m;
    return m.v = x, m;
  }
  static ModInt inv(const ModInt &x) { return make(inverse(x.v, mod)); }
  static uint inverse(int a, int m) {
    int u[] = {a, 1, 0}, v[] = {m, 0, 1}, t;
    while (*v) {
      t = *u / *v;
      swap(u[0] -= t * v[0], v[0]), swap(u[1] -= t * v[1], v[1]),
          swap(u[2] -= t * v[2], v[2]);
    }
    return (u[1] % m + m) % m;
  }

public:
  ModInt() : v{0} {}
  ModInt(const long long val) : v{norm(val % mod + mod)} {}
  ModInt(const ModInt<mod> &n) : v{n()} {}
  explicit operator bool() const noexcept { return v != 0; }
  bool operator!() const noexcept { return !static_cast<bool>(*this); }
  ModInt &operator=(const ModInt &n) { return v = n(), (*this); }
  ModInt &operator=(const long long val) {
    return v = norm(val % mod + mod), (*this);
  }
  ModInt operator+() const { return *this; }
  ModInt operator-() const { return v == 0 ? make(0) : make(mod - v); }
  ModInt operator+(const ModInt &val) const { return make(norm(v + val())); }
  ModInt operator-(const ModInt &val) const {
    return make(norm(v + mod - val()));
  }
  ModInt operator*(const ModInt &val) const {
    return make((long long)v * val() % mod);
  }
  ModInt operator/(const ModInt &val) const { return *this * inv(val); }
  ModInt &operator+=(const ModInt &val) { return *this = *this + val; }
  ModInt &operator-=(const ModInt &val) { return *this = *this - val; }
  ModInt &operator*=(const ModInt &val) { return *this = *this * val; }
  ModInt &operator/=(const ModInt &val) { return *this = *this / val; }
  ModInt operator+(const long long val) const { return ModInt{v + val}; }
  ModInt operator-(const long long val) const { return ModInt{v - val}; }
  ModInt operator*(const long long val) const {
    return ModInt{(long long)v * (val % mod)};
  }
  ModInt operator/(const long long val) const {
    return ModInt{(long long)v * inv(val)};
  }
  ModInt &operator+=(const long long val) { return *this = *this + val; }
  ModInt &operator-=(const long long val) { return *this = *this - val; }
  ModInt &operator*=(const long long val) { return *this = *this * val; }
  ModInt &operator/=(const long long val) { return *this = *this / val; }
  bool operator==(const ModInt &val) const { return v == val.v; }
  bool operator!=(const ModInt &val) const { return !(*this == val); }
  bool operator==(const long long val) const {
    return v == norm(val % mod + mod);
  }
  bool operator!=(const long long val) const { return !(*this == val); }
  uint operator()() const { return v; }
  friend ModInt operator+(const long long val, const ModInt &n) {
    return n + val;
  }
  friend ModInt operator-(const long long val, const ModInt &n) {
    return ModInt{val - n()};
  }
  friend ModInt operator*(const long long val, const ModInt &n) {
    return n * val;
  }
  friend ModInt operator/(const long long val, const ModInt &n) {
    return ModInt{val} / n;
  }
  friend bool operator==(const long long val, const ModInt &n) {
    return n == val;
  }
  friend bool operator!=(const long long val, const ModInt &n) {
    return !(val == n);
  }
  friend istream &operator>>(istream &is, ModInt &n) {
    uint v;
    return is >> v, n = v, is;
  }
  friend ostream &operator<<(ostream &os, const ModInt &n) {
    return (os << n());
  }
  friend ModInt pow(ModInt x, long long n) {
    ModInt ans = 1;
    while (n) {
      if (n & 1)
        ans *= x;
      x *= x, n >>= 1;
    }
    return ans;
  }
};

using mod = ModInt<MOD>;

mod inv[MAX_N], fac[MAX_N], finv[MAX_N];

void make() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX_N; i++) {
    inv[i] = MOD - inv[MOD % i] * (MOD / i);
    fac[i] = fac[i - 1] * i;
    finv[i] = finv[i - 1] * inv[i];
  }
}

mod comb(int a, int b) {
  if (a < b)
    return 0;
  return fac[a] * finv[b] * finv[a - b];
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n, a, b, K;
  cin >> n >> a >> b >> K;
  mod ans = 0;
  make();
  rep(i, n + 1) {
    if (K < i * a)
      break;
    if ((K - i * a) % b == 0) {
      ll j = (K - i * a) / b;
      ans += comb(n, i) * comb(n, j);
    }
  }
  cout << ans << "\n";
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 998244353
#define EPS 1e-10
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; --i)
#define srep(i, s, t) for (int i = (int)(s); i < (int)(t); ++i)
#define each(a, b) for (auto &(a) : (b))
#define all(v) (v).begin(), (v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)), v.erase(unique(all(v)), v.end())
#define cmx(x, y) x = max(x, y)
#define cmn(x, y) x = min(x, y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout << #x << " = " << (x) << endl
#define sar(a, n)                                                              \
  cout << #a << ":";                                                           \
  rep(pachico, n) cout << " " << a[pachico];                                   \
  cout << endl

using namespace std;

template <typename S, typename T> auto &operator<<(ostream &o, pair<S, T> p) {
  return o << "{" << p.fi << "," << p.se << "}";
}
template <typename T> auto &operator<<(ostream &o, set<T> s) {
  for (auto &e : s)
    o << e << " ";
  return o;
}
template <typename S, typename T, typename U>
auto &operator<<(ostream &o, priority_queue<S, T, U> q) {
  while (!q.empty())
    o << q.top() << " ", q.pop();
  return o;
}
template <typename K, typename T> auto &operator<<(ostream &o, map<K, T> m) {
  for (auto &e : m)
    o << e << " ";
  return o;
}
template <typename T> auto &operator<<(ostream &o, vector<T> v) {
  for (auto &e : v)
    o << e << " ";
  return o;
}
void ashow() { cout << endl; }
template <typename T, typename... A> void ashow(T t, A... a) {
  cout << t << " ";
  ashow(a...);
}

typedef pair<int, int> P;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<P> vp;
typedef vector<double> vd;
typedef vector<string> vs;

const int MAX_N = 300005;

template <uint mod> class ModInt {
private:
  uint v;
  static uint norm(const uint &x) { return x < mod ? x : x - mod; }
  static ModInt make(const uint &x) {
    ModInt m;
    return m.v = x, m;
  }
  static ModInt inv(const ModInt &x) { return make(inverse(x.v, mod)); }
  static uint inverse(int a, int m) {
    int u[] = {a, 1, 0}, v[] = {m, 0, 1}, t;
    while (*v) {
      t = *u / *v;
      swap(u[0] -= t * v[0], v[0]), swap(u[1] -= t * v[1], v[1]),
          swap(u[2] -= t * v[2], v[2]);
    }
    return (u[1] % m + m) % m;
  }

public:
  ModInt() : v{0} {}
  ModInt(const long long val) : v{norm(val % mod + mod)} {}
  ModInt(const ModInt<mod> &n) : v{n()} {}
  explicit operator bool() const noexcept { return v != 0; }
  bool operator!() const noexcept { return !static_cast<bool>(*this); }
  ModInt &operator=(const ModInt &n) { return v = n(), (*this); }
  ModInt &operator=(const long long val) {
    return v = norm(val % mod + mod), (*this);
  }
  ModInt operator+() const { return *this; }
  ModInt operator-() const { return v == 0 ? make(0) : make(mod - v); }
  ModInt operator+(const ModInt &val) const { return make(norm(v + val())); }
  ModInt operator-(const ModInt &val) const {
    return make(norm(v + mod - val()));
  }
  ModInt operator*(const ModInt &val) const {
    return make((long long)v * val() % mod);
  }
  ModInt operator/(const ModInt &val) const { return *this * inv(val); }
  ModInt &operator+=(const ModInt &val) { return *this = *this + val; }
  ModInt &operator-=(const ModInt &val) { return *this = *this - val; }
  ModInt &operator*=(const ModInt &val) { return *this = *this * val; }
  ModInt &operator/=(const ModInt &val) { return *this = *this / val; }
  ModInt operator+(const long long val) const { return ModInt{v + val}; }
  ModInt operator-(const long long val) const { return ModInt{v - val}; }
  ModInt operator*(const long long val) const {
    return ModInt{(long long)v * (val % mod)};
  }
  ModInt operator/(const long long val) const {
    return ModInt{(long long)v * inv(val)};
  }
  ModInt &operator+=(const long long val) { return *this = *this + val; }
  ModInt &operator-=(const long long val) { return *this = *this - val; }
  ModInt &operator*=(const long long val) { return *this = *this * val; }
  ModInt &operator/=(const long long val) { return *this = *this / val; }
  bool operator==(const ModInt &val) const { return v == val.v; }
  bool operator!=(const ModInt &val) const { return !(*this == val); }
  bool operator==(const long long val) const {
    return v == norm(val % mod + mod);
  }
  bool operator!=(const long long val) const { return !(*this == val); }
  uint operator()() const { return v; }
  friend ModInt operator+(const long long val, const ModInt &n) {
    return n + val;
  }
  friend ModInt operator-(const long long val, const ModInt &n) {
    return ModInt{val - n()};
  }
  friend ModInt operator*(const long long val, const ModInt &n) {
    return n * val;
  }
  friend ModInt operator/(const long long val, const ModInt &n) {
    return ModInt{val} / n;
  }
  friend bool operator==(const long long val, const ModInt &n) {
    return n == val;
  }
  friend bool operator!=(const long long val, const ModInt &n) {
    return !(val == n);
  }
  friend istream &operator>>(istream &is, ModInt &n) {
    uint v;
    return is >> v, n = v, is;
  }
  friend ostream &operator<<(ostream &os, const ModInt &n) {
    return (os << n());
  }
  friend ModInt pow(ModInt x, long long n) {
    ModInt ans = 1;
    while (n) {
      if (n & 1)
        ans *= x;
      x *= x, n >>= 1;
    }
    return ans;
  }
};

using mod = ModInt<MOD>;

mod inv[MAX_N], fac[MAX_N], finv[MAX_N];

void make() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX_N; i++) {
    inv[i] = MOD - inv[MOD % i] * (MOD / i);
    fac[i] = fac[i - 1] * i;
    finv[i] = finv[i - 1] * inv[i];
  }
}

mod comb(int a, int b) {
  if (a < b)
    return 0;
  return fac[a] * finv[b] * finv[a - b];
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n, a, b, K;
  cin >> n >> a >> b >> K;
  mod ans = 0;
  make();
  rep(i, n + 1) {
    if (K < i * a)
      break;
    if ((K - i * a) % b == 0) {
      ll j = (K - i * a) / b;
      ans += comb(n, i) * comb(n, j);
    }
  }
  cout << ans << "\n";
  return 0;
}