#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 2e3 + 2;
const int mod = 1e9 + 7;
int dp[N][N];
int Add(int a, int b) {
a += b;
if (a >= mod) a -= mod;
return a;
}
int Mul(int a, int b) {
ll c = a; c *= b; c %= mod;
return c;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n, a, b;
cin >> n >> a >> b;
dp[1][1] = 1;
for (int i = 2; i <= n; i++) {
for (int j = 1; j <= n; j++) {
if (i == a || i == b) {
dp[i][j] = Add(dp[i - 1][j - 1], dp[i - 1][j]);
continue;
}
dp[i][j] = Add(dp[i][j], Mul(j, dp[i - 1][j + 1]));
int k = j - (i > a) - (i > b);
dp[i][j] = Add(dp[i][j], Mul(k, dp[i - 1][j - 1]));
}
}
cout << dp[n][1] << en;
return 0;
}
