#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 505;
int A[N][N][N], D[N][N][N];
int n, s, t;
int main() {
cin.tie(0)->sync_with_stdio(0); cout.tie(0);
cin >> n >> s >> t;
if (s > t) swap(s, t);
A[2][1][2] = D[2][2][1] = 1;
for (int i = 3; i <= n; ++i) {
for (int s = 1; s <= i; ++s) {
for (int t = i; t; --t) {
if (s == t) continue;
if (s > t) {
A[i][s][t] = A[i][t][s];
D[i][s][t] = D[i][t][s];
continue;
}
for (int j = s; j <= i - 1; ++j) {
A[i][s][t] += D[i - 1][j][t - 1];
}
for (int j = 1; j < s; ++j) {
D[i][s][t] += A[i - 1][j][t - 1];
}
// cerr << i << ' ' << s << ' ' << t << ' ' << A[i][s][t] << ' ' << D[i][s][t] << '\n';
}
}
}
cout << A[n][s][t] + D[n][s][t];
return 0;
}
