#include <bits/stdc++.h>
using namespace std;
const int nax=2e3+5;
const int MOD=1e9+7;
long long dp[nax][nax];
int main() {
/*#ifndef ONLINE_JUDGE
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
#endif*/
int n,l,r;
cin>>n>>l>>r;
if(l>r) swap(l,r);
dp[0][0]=1;
for (int i = 1; i <= n; ++i)
{
for (int j = 0; j <= n; ++j)
{
if(i==l||i==r){
dp[i][j]+=dp[i-1][j+1]*(j+1);
if(j>0) dp[i][j]+=dp[i-1][j-1];
}else{
if(j>1) dp[i][j]+=dp[i-1][j-2];
dp[i][j]+=dp[i-1][j+2]*(j+1)*(j+2)/2;
}
//cout << i << " "<<j<<" "<<dp[i][j]<<endl;
dp[i][j]%=MOD;
}
}
cout <<dp[n-1][0]<<endl;
}
