#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const int MOD = 1000000007;
int add(int a, int b){ a += b; if(a >= MOD) a -= MOD; return a; }
int mul(int a, int b){ return (1LL*a*b)%MOD; }
int dp[2005][2005];
int main(){
ios_base::sync_with_stdio(false), cin.tie(0);
cout.precision(10);
cout << fixed;
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][j], add(dp[i-1][j-1], dp[i-1][j]));
else{
dp[i][j] = add(dp[i][j], mul(j, dp[i-1][j+1]));
int mesta = j;
if(i > a) mesta--;
if(i > b) mesta--;
dp[i][j] = add(dp[i][j], mul(mesta, dp[i-1][j-1]));
}
}
}
cout << dp[n][1] << "\n";
return 0;
}
