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#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx")
#pragma GCC optimize("unroll-loops")    
#include <bits/stdc++.h>
#define pb push_back
#define x first
#define y second
#define mp make_pair
#define len(a) int(a.size())
#define files(FILENAME) read(FILENAME); write(FILENAME)
#define read(FILENAME) freopen((string(FILENAME) + ".in").c_str(), "r", stdin)
#define write(FILENAME) freopen((string(FILENAME) + ".out").c_str(), "w", stdout)
using namespace std;
        
template<typename T1, typename T2>inline void chkmin(T1 &x, T2 y) { if (x > y) x = y; }
template<typename T1, typename T2>inline void chkmax(T1 &x, T2 y) { if (x < y) x = y; } 
template<typename T, typename U> inline ostream &operator<< (ostream &_out, const pair<T, U> &_p) { _out << _p.first << ' ' << _p.second; return _out; }
template<typename T, typename U> inline istream &operator>> (istream &_in, pair<T, U> &_p) { _in >> _p.first >> _p.second; return _in; }
template<typename T> inline ostream &operator<< (ostream &_out, const vector<T> &_v) { if (_v.empty()) { return _out; } _out << _v.front(); for (auto _it = ++_v.begin(); _it != _v.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T> inline istream &operator>> (istream &_in, vector<T> &_v) { for (auto &_i : _v) { _in >> _i; } return _in; }
template<typename T> inline ostream &operator<< (ostream &_out, const set<T> &_s) { if (_s.empty()) { return _out; } _out << *_s.begin(); for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T> inline ostream &operator<< (ostream &_out, const multiset<T> &_s) { if (_s.empty()) { return _out; } _out << *_s.begin(); for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T> inline ostream &operator<< (ostream &_out, const unordered_set<T> &_s) { if (_s.empty()) { return _out; } _out << *_s.begin(); for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T> inline ostream &operator<< (ostream &_out, const unordered_multiset<T> &_s) { if (_s.empty()) { return _out; } _out << *_s.begin(); for (auto _it = ++_s.begin(); _it != _s.end(); ++_it) { _out << ' ' << *_it; } return _out; }
template<typename T, typename U> inline ostream &operator<< (ostream &_out, const map<T, U> &_m) { if (_m.empty()) { return _out; } _out << '(' << _m.begin()->first << ": " << _m.begin()->second << ')'; for (auto _it = ++_m.begin(); _it != _m.end(); ++_it) { _out << ", (" << _it->first << ": " << _it->second << ')'; } return _out; }
template<typename T, typename U> inline ostream &operator<< (ostream &_out, const unordered_map<T, U> &_m) { if (_m.empty()) { return _out; } _out << '(' << _m.begin()->first << ": " << _m.begin()->second << ')'; for (auto _it = ++_m.begin(); _it != _m.end(); ++_it) { _out << ", (" << _it->first << ": " << _it->second << ')'; } return _out; }
        
typedef long long base; 
typedef pair<int, int> point;      
typedef complex<double> comp;

const int p = 1e9 + 7;

int sum(int a, int b) {
    a += b;
    return a < p ? a : a - p;
}

int mul(long long a, int b) {
    return a * b % p;
}

int powx(int a, int b) {
    int ans = 1;
    while (b) {
        if (b & 1) ans = mul(ans, a);
        a = mul(a, a);
        b >>= 1;
    }
    return ans;
}

int n, m;
int dp[2002][2002];
int f[2][2002 * 2002];

int cnk(int n, int k) {
    return mul(f[0][n], mul(f[1][n - k], f[1][k]));
}

int main() {
    ios::sync_with_stdio(0);
    cin >> n >> m;
    f[0][0] = 1;
    for (int i = 1; i <= n * m; ++i) {
        f[0][i] = mul(f[0][i - 1], i);
    }
    f[1][n * m] = powx(f[0][n * m], p - 2);
    for (int i = n * m; i >= 1; --i) {
        f[1][i - 1] = mul(f[1][i], i);
    }
    if (m == 1) {
        cout << 1 << '\n';
        return 0;
    }
    dp[0][0] = 1;
    for (int i = 0; i <= n; ++i) {
        for (int j = 0; j < n; ++j) {
            // if (dp[i][j] == 0) break;
            dp[i + 1][j] = sum(dp[i + 1][j], dp[i][j]);
            if (i > j) {
                int sz = n * m - i - j * (m - 1);
                dp[i][j + 1] = sum(dp[i][j + 1], mul(dp[i][j], cnk(sz - 1, m - 2)));
            }
        }
    }
    cout << mul(f[0][n], dp[n][n]) << '\n';
}  

Measured memory_bytes: 47232