#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint MOD = 1000000007;
int N, S, T;
lint memo[2005][2005];
lint dp(int n, int comp) {
if (comp < 0) {
return 0;
}
if (n == N) {
return comp == 0;
}
if (memo[n][comp] != -1) {
return memo[n][comp];
}
lint &res = memo[n][comp] = 0;
if (n == S || n == T) {
res += dp(n + 1, comp); // add S or T as new component
res += comp * dp(n + 1, comp - 1); // add S or T as beginning / end. After that we cannot modify it anymore, so ignore it (AKA delete it).
} else {
res += dp(n + 1, comp + 1); // add new component
res += comp * (comp - 1) * dp(n + 1, comp - 1); // join two components
if (n > S) {
res += comp * dp(n + 1, comp - 1); // append S to a component, and it cannot be modified further
}
if (n > T) {
res += comp * dp(n + 1, comp - 1); // append T to a component, and it cannot be modified further
}
}
res %= MOD;
return res;
}
int main() {
memset(memo, -1, sizeof(memo));
cin >> N >> S >> T;
S--, T--;
cout << dp(0, 0) << "\n";
return 0;
}
