#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
#define pb push_back
#define rsz resize
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
using pi = pair<int,int>;
#define f first
#define s second
#define mp make_pair
const int MOD = (int) 1e9 + 7;
ll dp[2005][2005];
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
int n, a, b; cin >> n >> a >> b;
dp[0][0] = 1;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
if (i == a || i == b) {
dp[i][j] = dp[i - 1][j] + dp[i - 1][j - 1];
}
else {
dp[i][j] = ((j * dp[i - 1][j + 1]) % MOD) + (((j - (i > a) - (i > b)) * dp[i - 1][j - 1]) % MOD) % MOD;
}
}
}
cout << dp[n][1] << '\n';
}
