#pragma GCC optimize("O3", "inline")
#include <bits/stdc++.h>
using namespace std;
#define ins insert
#define pb push_back
#define int long long int
#define pii pair<int, int>
#define endl '\n'
#define drop(x) cout<<(x)<<endl; return;
#define all(x) x.begin(),x.end()
const int mod = 1e9 +7, sze = 1e5+10, inf = 2e18, prime = 23;
int dp[2005][2005];
void mal(){
dp[1][1]=1;
int n,a,b;cin>>n>>a>>b;
for(int i=2;i<=n;i++){
for(int j=1;j<=n;j++){
if(i==a || i==b){
dp[i][j] = (dp[i][j] + dp[i-1][j-1] + dp[i-1][j] +mod)%mod;
}
else{
dp[i][j]= (dp[i-1][j+1]*j + dp[i][j] + mod)%mod;
dp[i][j] = (dp[i][j] + dp[i-1][j-1] * (j - (i>a) - (i>b)) + mod)%mod; // a ni gormusuk, a dan arxaya qoyammariq, b ni gormusuk, b den arxaya qoyammariq, 2 hours
}
}
}
drop(dp[n][1]);
}
signed main() {
cin.tie(0)->sync_with_stdio(0);
int tt = 1;
// cin>>tt;
while(tt--){
mal();
}
}
