#include <bits/stdc++.h> using namespace std; #define endl '\n' #define int long long #define ll long long #define ull unsigned long long #define lb lower_bound #define ub upper_bound #define IOS ios::sync_with_stdio(false), cin.tie(0), cout.tie(0) int gcd(int a, int b){ return __gcd(a, b); } int lcm(int a, int b){ return a / gcd(a, b) * b; } int dx[] = {-1, -1, -1, 0, 0, 1, 1, 1}; int dy[] = {-1, 0, 1, -1, 1, -1, 0, 1}; void solve(){ int n, a, b; cin >> n >> a >> b; vector<int> vt; for (int i = 1; i <= n; i++ ){ if(i != a && i != b)vt.push_back(i); } int ans = 0; do{ bool ok = true; if(vt[0] < a){ for (int i = 1; i < vt.size(); i++ ){ if(i % 2 != 0){ if(vt[i] <= vt[i - 1]){ ok = false; break; } } else{ if(vt[i] >= vt[i - 1]){ ok = false; break; } } } if(n % 2 == 0){ if(vt[vt.size() - 1] <= b) ok = false; } else{ if(vt[vt.size() - 1] >= b) ok = false; } } else{ for (int i = 1; i < vt.size(); i++ ){ if(i % 2 == 0){ if(vt[i] <= vt[i - 1]){ ok = false; break; } } else{ if(vt[i] >= vt[i - 1]){ ok = false; break; } } } if(n % 2 != 0){ if(vt[vt.size() - 1] <= b) ok = false; } else{ if(vt[vt.size() - 1] >= b) ok = false; } } if(ok)ans++; }while(next_permutation(vt.begin(), vt.end())); cout << ans << endl; } signed main(){ IOS; int t = 1; //cin >> t; while (t--){ solve(); } }