#include <bits/stdc++.h>
using namespace std;
#define ld long double
#define int long long
#define endl "\n"
const int N = 2000,mod = 1e9 + 7;
int dp[N + 1][N + 1][2][2];
int n,a,b;
int f(int curr,int comp,bool front,bool back) {
if(curr == n + 1) {
return (comp == 1);
}
if(dp[curr][comp][front][back] != -1) return dp[curr][comp][front][back];
if(curr == a) {
int res = 0;
if(!front) {
res = (res + f(curr + 1,comp,1,back))%mod;
res = (res + f(curr + 1,comp + 1,0,back))%mod;
}
return dp[curr][comp][front][back] = res;
}
if(curr == b) {
int res = 0;
if(!back) {
res = (res + f(curr + 1,comp + 1,front,0))%mod;
res = (res + f(curr + 1,comp,front,1))%mod;
}
return dp[curr][comp][front][back] = res;
}
int res = 0;
if(comp > 1) {
res = (res + (f(curr + 1,comp - 1,front,back) * (comp - 1))%mod)%mod;
}
res = (res + (f(curr + 1,comp + 1,front,back) * (comp - 1))%mod)%mod;
if(curr < a) {
if(!front) {
res = (res + f(curr + 1,comp + 1,0,back))%mod;
res = (res + f(curr + 1,comp,1,back))%mod;
}
}
if(curr < b) {
if(!back) {
res = (res + f(curr + 1,comp + 1,front,0))%mod;
res = (res + f(curr + 1,comp,front,1))%mod;
}
}
return dp[curr][comp][front][back] = res;
}
signed main() {
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
cin>>n>>a>>b;
memset(dp,-1,sizeof(dp));
cout<<f(2,1,0,0)<<endl;
vector<int> asd;
for(int i = 1;i <= n;i++) {
asd.push_back(i);
}
return 0;
}
