#include<bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define endl '\n'
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll, ll> pll;
int mod = 1e9 + 7;
int add(int a, int b) {
a += b;
if (a < 0) a += mod;
if (a >= mod) a -= mod;
return a;
}
int mul(int a, int b) {
return 1ll*a*b%mod;
}
const int N = 2050;
int n, cs, cf;
int dp[N][N], pd[N][N];
void solve() {
cin >> n >> cs >> cf;
if (cs > cf) swap(cs, cf);
pd[2][2] = 1;
for (int i = 3; i <= n; i++) {
if (i&1) for (int j = 1; j <= i-1; j++) pd[i][1] = add(pd[i][1], pd[i-1][j]);
for (int j = 2; j <= i; j++) {
pd[i][j] = add(pd[i][j-1], (i&1? -1:1)*pd[i-1][j-1]);
}
pd[i][1] = 0;
}
for (int i = 2; i <= n; i++) {
if (i > n-cf) dp[i][1] = pd[i][i-n+cf];
dp[i][2] = add(dp[i][1], dp[i-1][1]);
for (int j = 3; j <= i; j++) {
dp[i][j] = add(add(dp[i][j-1], dp[i][j-1]), add(dp[i][j-2], -dp[i-2][j-2]));
}
}
cout << dp[n][cs] << endl;
}
int main() {
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
solve();
return 0;
}
