#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
#include <random>
#include <chrono>
#include <fstream>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
const int MOD = 1000000007;
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, a, b;
cin>>n>>a>>b;
vector<vector<int> > dp(n+1, vector<int>(n+2, 0));
dp[0][0]=1;
for (int i=1; i<=n; ++i)for (int j=1; j<=i; ++j){
if (i==a||i==b)dp[i][j]=(dp[i][j]+dp[i-1][j-1]+dp[i-1][j])%MOD;
else dp[i][j]=(dp[i][j]+j*dp[i-1][j+1]+max(0ll, j-(i>a)-(i>b))*dp[i-1][j-1])%MOD;
}
cout<<dp[n][1];
}
