#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
constexpr bool typetest = 0;
constexpr int N = 2e3 + 2;
int n, cs, cf, v;
int dp[N][N], f1[N][N];
void Read()
{
cin >> n >> cs >> cf;
if (cs > cf)
swap(cs, cf);
v = n - cf;
}
ll f(int n, int i)
{
if (dp[n][i] != -1)
return dp[n][i];
if (i == 1)
return dp[n][i] = f1[n][n - v];
if (i == 2)
return dp[n][i] = f1[n][n - v] + f1[n - 1][n - 1 - v];
return dp[n][i] = 2 * f(n, i - 1) - f(n, i - 2) - f(n - 2, i - 2);
}
void Solve()
{
f1[1][1] = 1;
for (int i = 2; i <= n; ++i)
{
if (i & 1)
f1[i][2] = 1;
for (int j = 2; j <= i; ++j)
f1[i][j] += (i & 1) ? f1[i][j - 1] - f1[i - 1][j - 1] : f1[i][j - 1] + f1[i - 1][j - 1];
}
memset(dp, -1, sizeof dp);
cout << f(n, cs);
}
int32_t main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t(1);
if (typetest)
cin >> t;
for (int _ = 1; _ <= t; ++_)
{
Read();
Solve();
}
}
