// Starcraft 2 enjoyer //
#include <bits/stdc++.h>
// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
using namespace std;
#define LSOne(X) ((X) & -(X))
const int N = 2e3 + 5;
const int K = 1e2 + 5;
const int LG = 20;
const int INF = 1e9 + 5;
const int B = 1000;
const int MOD = 1e9 + 7;
int n, a, b;
long long dp[N][N];
inline void solve()
{
cin >> n >> a >> b;
dp[0][0] = 1;
for (int x = 1; x <= n; x++)
{
for (int y = 0; y <= x; y++)
{
if (x == a || x == b)
{
dp[x][y] = dp[x - 1][y];
}
else
{
dp[x][y] += 1LL * (y - 1) * dp[x - 1][y + 1];
if (y > 0)
dp[x][y] += 1LL * (y + 1) * dp[x - 1][y - 1];
dp[x][y] += 1LL * y * dp[x - 1][y];
}
dp[x][y] %= MOD;
// cout << dp[x][y] << " ";
}
// cout << "\n";
}
cout << dp[n][1] << "\n";
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
// cin >> t;
for (int x = 1; x <= t; x++)
{
solve();
}
return 0;
}
