// Code by Parsa Eslami
#include <bits/stdc++.h>
#define int long long
#define FOR(i,a,b) for(int i=a;i<=b;i++)
#define FORR(i,a,b) for(int i=a;i>=b;i--)
#define S second
#define F first
#define pb push_back
#define SZ(x) (int)x.size()
#define all(x) x.begin(),x.end()
#define err(x) cout<<#x<<": "<<x<<'\n';
using namespace std;
const int N=2000+5;
const int MOD=1e9+7;
int C[N][N];
int dp[N][N][2];//st t
int ps[N][2];//st
void pre(){
FOR(i,0,N-1) C[0][i]=1;
FOR(i,1,N-1) FOR(j,i,N-1) C[i][j]=(C[i][j-1]+C[i-1][j-1])%MOD;
dp[1][1][0]=1;
dp[1][1][1]=1;
FOR(i0,0,1) FOR(st,1,N-1){
ps[st][i0]=ps[st-1][i0]+dp[st][1][i0];
}
FOR(t,2,N-1){
FOR(st,1,t){
dp[st][t][0]=ps[st-1][1]%MOD;
dp[st][t][1]=(ps[t][0]-ps[st-1][0])%MOD;
}
FOR(i0,0,1) FOR(st,1,N-1){
ps[st][i0]=(ps[st-1][i0]+dp[st][t][i0])%MOD;
}
}
}
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(0);
pre();
int ans=0;
int n,st,en; cin>>n>>st>>en;
if(en<st) swap(en,st);
if(st==1){
ans=dp[en-1][n-1][(n&1)];
}else{
FOR(i,0,st-2) FOR(j,0,en-st-1) FOR(w,0,n-en){
int t1=st-2-i;
int t2=en-st-1-j;
int t3=n-en-w;
ans+=((((C[i][st-2]*C[j][en-st-1])%MOD)*C[w][n-en]%MOD)*dp[i+1][(i+j+w+2-1)][(i+j+w+2)&1]%MOD)*dp[t1+t2+1][t1+t2+t3+2-1][(t1+t2+t3)&1];
ans%=MOD;
}
}
ans=((ans%MOD)+MOD)%MOD;
cout<<ans<<'\n';
return 0;
}
