LINEUP

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

int const N = 2009;
int const mod = 1e9 + 7;
typedef pair <ll, ll> ii;

long long n, p, q, C[N][N], dp[N][N];
long long res;

long long Count (int x, int y) {
    return dp[x - 1][y - 1];
}

void Sub2() {
    dp[1][1] = 1;
    for (int i = 2; i <= n; i++)
        for (int j = 1; j <= min((ll) i, p); j++)
            dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j] * (i - 1)) % mod;

    cout << dp[n - 1][p - 1];
}

long long f[509][509], g[509][509];

void Sub3() {
    f[1][1] = 1;

    for (int i = 2; i <= n; i++) {
        for (int pp = 0; pp <= p; pp++)
           for (int qq = 0; qq <= q; qq++)
                g[pp][qq] = f[pp][qq];

        for (int pp = 1; pp <= p; pp++)
           for (int qq = 1; qq <= q; qq++)
                f[pp][qq] = (g[pp - 1][qq] + g[pp][qq - 1] + g[pp][qq] * (i - 2)) % mod;
    }

    cout << f[p][q];
}


void Sub4() {
    for (int i = 0; i <= 2000; i++)
        C[0][i] = 1;
    for (int i = 1; i <= 2000; i++)
        for (int j = 1; j <= i; j++)
            C[j][i] = (C[j][i - 1] + C[j - 1][i - 1]) % mod;

    dp[1][1] = dp[0][0] = 1;
    for (int i = 2; i <= n; i++)
        for (int j = 1; j <= min((ll) i, max(p, q)); j++)
            dp[i][j] = (dp[i - 1][j - 1] + dp[i - 1][j] * (i - 1)) % mod;

    for (int i = 1; i <= n; i++)
        res = (res + (C[i - 1][n - 1] * Count(i, p) % mod) * Count(n - i + 1, q) % mod) % mod;

    cout << res;
}

int main ()
{
    cin >> n >> p >> q;

    if (q == 1) Sub2();
    else if (n <= 500) Sub3();
    else Sub4();

    return 0;
}