Problem p02634 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define FOR(var, begin, end) for (int var = (begin); var <= (end); var++)
#define RFOR(var, begin, end) for (int var = (begin); var >= (end); var--)
#define REP(var, length) FOR(var, 0, length - 1)
#define RREP(var, length) RFOR(var, length - 1, 0)
#define EACH(value, var) for (auto value : var)
#define SORT(var) sort(var.begin(), var.end())
#define REVERSE(var) reverse(var.begin(), var.end())
#define RSORT(var)                                                             \
  SORT(var);                                                                   \
  REVERSE(var)
#define OPTIMIZE_STDIO                                                         \
  ios::sync_with_stdio(false);                                                 \
  cin.tie(0);                                                                  \
  cout.precision(10);                                                          \
  cout << fixed
#define endl '\n'

const int INF = 1e9;
const int MOD = 998244353;
const ll LINF = 1e18;

struct mint {
  ll x;
  mint() : x(0) {}
  mint(ll x) : x((x % MOD + MOD) % MOD) {}
  mint &operator+=(const mint &r) {
    if ((x += r.x) >= MOD) {
      x -= MOD;
    }
    return *this;
  }
  mint &operator-=(const mint &r) {
    if ((x -= r.x) < 0) {
      x += MOD;
    }
    return *this;
  }
  mint &operator*=(const mint &r) {
    if ((x *= r.x) > MOD) {
      x %= MOD;
    }
    return *this;
  }
  mint &operator++() {
    if ((++x) >= MOD) {
      x -= MOD;
    }
    return *this;
  }
  mint operator++(int) {
    mint ret = x;
    if ((++x) >= MOD) {
      x -= MOD;
    }
    return ret;
  }
  mint &operator--() {
    if ((--x) < 0) {
      x += MOD;
    }
    return *this;
  }
  mint operator--(int) {
    mint ret = x;
    if ((--x) < 0) {
      x += MOD;
    }
    return ret;
  }
  mint operator+(const mint &r) {
    mint ret;
    return ret = x + r.x;
  }
  mint operator-(const mint &r) {
    mint ret;
    return ret = x - r.x;
  }
  mint operator*(const mint &r) {
    mint ret;
    return ret = x * r.x;
  }
  mint operator-() { return mint() - *this; }
  mint pow(ll t) {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
  bool operator<(const mint &a) { return x < a.x; }
  bool operator>(const mint &a) { return x > a.x; }
  bool operator<=(const mint &a) { return x <= a.x; }
  bool operator>=(const mint &a) { return x >= a.x; }
  bool operator==(const mint &a) { return x == a.x; }
  bool operator!=(const mint &a) { return x != a.x; }
};
ostream &operator<<(ostream &os, const mint &r) {
  os << r.x;
  return os;
}
ostream &operator>>(ostream &os, const mint &r) {
  os >> r.x;
  return os;
}

mint dp[3001][3001];

void solve(istream &cin, ostream &cout) {
  ll a, b, c, d;
  cin >> a >> b >> c >> d;
  dp[a][b] = 1;
  FOR(i, a, c + 1) {
    FOR(j, b, d + 1) {
      if (i > a)
        dp[i][j] += dp[i - 1][j] * j;
      if (j > b)
        dp[i][j] += dp[i][j - 1] * i;
      if (i > a && j > b)
        dp[i][j] -= dp[i - 1][j - 1] * (i - 1) * (j - 1);
    }
  }
  cout << dp[c][d] << endl;
}

#ifndef TEST
int main() {
  OPTIMIZE_STDIO;
  solve(cin, cout);
  return 0;
}
#endif


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define FOR(var, begin, end) for (int var = (begin); var <= (end); var++)
#define RFOR(var, begin, end) for (int var = (begin); var >= (end); var--)
#define REP(var, length) FOR(var, 0, length - 1)
#define RREP(var, length) RFOR(var, length - 1, 0)
#define EACH(value, var) for (auto value : var)
#define SORT(var) sort(var.begin(), var.end())
#define REVERSE(var) reverse(var.begin(), var.end())
#define RSORT(var)                                                             \
  SORT(var);                                                                   \
  REVERSE(var)
#define OPTIMIZE_STDIO                                                         \
  ios::sync_with_stdio(false);                                                 \
  cin.tie(0);                                                                  \
  cout.precision(10);                                                          \
  cout << fixed
#define endl '\n'

const int INF = 1e9;
const int MOD = 998244353;
const ll LINF = 1e18;

struct mint {
  ll x;
  mint() : x(0) {}
  mint(ll x) : x((x % MOD + MOD) % MOD) {}
  mint &operator+=(const mint &r) {
    if ((x += r.x) >= MOD) {
      x -= MOD;
    }
    return *this;
  }
  mint &operator-=(const mint &r) {
    if ((x -= r.x) < 0) {
      x += MOD;
    }
    return *this;
  }
  mint &operator*=(const mint &r) {
    if ((x *= r.x) > MOD) {
      x %= MOD;
    }
    return *this;
  }
  mint &operator++() {
    if ((++x) >= MOD) {
      x -= MOD;
    }
    return *this;
  }
  mint operator++(int) {
    mint ret = x;
    if ((++x) >= MOD) {
      x -= MOD;
    }
    return ret;
  }
  mint &operator--() {
    if ((--x) < 0) {
      x += MOD;
    }
    return *this;
  }
  mint operator--(int) {
    mint ret = x;
    if ((--x) < 0) {
      x += MOD;
    }
    return ret;
  }
  mint operator+(const mint &r) {
    mint ret;
    return ret = x + r.x;
  }
  mint operator-(const mint &r) {
    mint ret;
    return ret = x - r.x;
  }
  mint operator*(const mint &r) {
    mint ret;
    return ret = x * r.x;
  }
  mint operator-() { return mint() - *this; }
  mint pow(ll t) {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
  bool operator<(const mint &a) { return x < a.x; }
  bool operator>(const mint &a) { return x > a.x; }
  bool operator<=(const mint &a) { return x <= a.x; }
  bool operator>=(const mint &a) { return x >= a.x; }
  bool operator==(const mint &a) { return x == a.x; }
  bool operator!=(const mint &a) { return x != a.x; }
};
ostream &operator<<(ostream &os, const mint &r) {
  os << r.x;
  return os;
}
ostream &operator>>(ostream &os, const mint &r) {
  os >> r.x;
  return os;
}

mint dp[3002][3002];

void solve(istream &cin, ostream &cout) {
  ll a, b, c, d;
  cin >> a >> b >> c >> d;
  dp[a][b] = 1;
  FOR(i, a, c + 1) {
    FOR(j, b, d + 1) {
      if (i > a)
        dp[i][j] += dp[i - 1][j] * j;
      if (j > b)
        dp[i][j] += dp[i][j - 1] * i;
      if (i > a && j > b)
        dp[i][j] -= dp[i - 1][j - 1] * (i - 1) * (j - 1);
    }
  }
  cout << dp[c][d] << endl;
}

#ifndef TEST
int main() {
  OPTIMIZE_STDIO;
  solve(cin, cout);
  return 0;
}
#endif