Language: C++

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

#define LL long long
typedef pair<int, int> pii;

template< typename T > inline void read(T &x)
{
    static char _c;
    static bool _f;

    x = 0;
    _f = 0;
    _c = getchar();

    while(_c < '0' || '9' < _c) {if(_c == '-') _f = true; _c = getchar();}
    while('0' <= _c && _c <= '9') {x = (x << 1) + (x << 3) + (_c & 15); _c = getchar();}
    if(_f) x = -x;
}

template < typename T > inline void Min(T &x, T y) {if(y < x) x = y;}
template < typename T > inline void Max(T &x, T y) {if(x < y) x = y;}


#define lowbit(x) ((x) & -(x))
#define lson l,mid,id<<1
#define rson mid+1,r,id<<1|1
#define ls id<<1
#define rs id<<1|1
#define MID(l,r) ((l)+(((r)-(l))>>1))
#define fi first
#define se second
#define mk make_pair
#define pb push_back

const int INF = 0x3f3f3f3f;
const double pi = (double) acos(-1.0);
const double eps = (double) 1e-8;
//const int MOD = (int) 1e9 + 7;
//const int MOD = (int) 998244353;
//int MOD = 998244353;
const int maxn = (int) 1e5 + 20;
const int maxm = (int) 1e6 + 20;

inline int sig(double x) {return x < -eps ? -1 : eps < x;}
LL fp(LL a, LL n, LL mod = MOD)
{
    if(n < 0) a = fp(a, mod - 2, mod), n = -n;
    LL res = 1; for(; n; n >>= 1, a = a * a % mod) if(n & 1) res = res * a % mod; return res;
}

struct Mint
{
    LL x;
    Mint() {x = 0;}
    Mint(int _x): x(_x) {}
    Mint(LL _x): x(_x) {}
    Mint operator - () const{
        return Mint(MOD - x);
    }
    Mint operator + (const Mint &rhs) const{
        LL res = x + rhs.x; if(res >= MOD) res -= MOD; return Mint(res);
    }
    Mint operator - (const Mint &rhs) const{
        LL res = x - rhs.x; if(res < 0) res += MOD; return Mint(res);
    }
    Mint operator * (const Mint &rhs) const{
        return Mint(x * rhs.x % MOD);
    }
    Mint operator / (const Mint &rhs) const{
        return Mint(x * fp(rhs.x, -1) % MOD);
    }
    bool operator == (const Mint &rhs) const{
        return x == rhs.x;
    }
    bool operator != (const Mint &rhs) const{
        return x != rhs.x;
    }
    friend ostream& operator << (ostream &out, const Mint &rhs){
        return out << rhs.x;
    }
    friend istream& operator >> (istream &in, Mint &rhs){
        return in >> rhs.x;
    }
};

int n, m;
Mint dp[6666][6666 + 6666];

void work()
{
    cin >>n >>m;
    MOD = m;

    int mid = 6666;
    dp[0][mid] = Mint(1);

    for(int i = 1; i <= n * 3; i++)
    {
        for(int j = mid - i / 2; j <= mid + i; j++)
        {
            dp[i][j] = dp[i - 1][j - 1];
            if(i >= 2) dp[i][j] = dp[i][j] + dp[i - 2][j + 1] * Mint(i - 1);
            if(i >= 3) dp[i][j] = dp[i][j] + dp[i - 3][j] * Mint(i - 1) * Mint(i - 2);
        }
    }

    Mint ans = Mint(0);
    for(int j = mid; j <= mid + n * 3; j++) ans = ans + dp[n * 3][j];
    cout <<ans <<endl;
}


int main(int argc, char **argv)
{
#ifdef yukihana0416
freopen("in.txt", "r", stdin);
//freopen("out.txt", "w", stdout);
#endif // yukihana0416
//    get_prime();
//    pre();
    int tc = 1;
//    read(tc);
    for(int ca = 1; ca <= tc; ca++)
    {
//        printf("Case #%d: ", ca);
        work();
    }
    return 0;
}


Compiler output:
a.cc:46:28: error: 'MOD' was not declared in this scope; did you mean 'MID'?
   46 | LL fp(LL a, LL n, LL mod = MOD)
      |                            ^~~
      |                            MID
a.cc: In member function 'Mint Mint::operator-() const':
a.cc:59:21: error: 'MOD' was not declared in this scope; did you mean 'MID'?
   59 |         return Mint(MOD - x);
      |                     ^~~
      |                     MID
a.cc: In member function 'Mint Mint::operator+(const Mint&) const':
a.cc:62:39: error: 'MOD' was not declared in this scope; did you mean 'MID'?
   62 |         LL res = x + rhs.x; if(res >= MOD) res -= MOD; return Mint(res);
      |                                       ^~~
      |                                       MID
a.cc: In member function 'Mint Mint::operator-(const Mint&) const':
a.cc:65:48: error: 'MOD' was not declared in this scope; did you mean 'MID'?
   65 |         LL res = x - rhs.x; if(res < 0) res += MOD; return Mint(res);
      |                                                ^~~
      |                                                MID
a.cc: In member function 'Mint Mint::operator*(const Mint&) const':
a.cc:68:33: error: 'MOD' was not declared in this scope; did you mean 'MID'?
   68 |         return Mint(x * rhs.x % MOD);
      |                                 ^~~
      |                                 MID
a.cc: In member function 'Mint Mint::operator/(const Mint&) const':
a.cc:71:41: error: 'MOD' was not declared in this scope; did you mean 'MID'?
   71 |         return Mint(x * fp(rhs.x, -1) % MOD);
      |                                         ^~~
      |                                         MID
a.cc: In function 'void work()':
a.cc:93:5: error: 'MOD' was not declared in this scope; did you mean 'MID'?
   93 |     MOD = m;
      |     ^~~
      |     MID