#pragma GCC optimize("O3") #include <bits/stdc++.h> using namespace std; #define F first #define S second #define int long long #define pb push_back #define all(v) v.begin(), v.end() #define rall(v) v.rbegin(), v.rend() #define endl "\n" #define Yes cout << "YES" << endl; #define No cout << "NO" << endl; #define mod(a) ((a % MOD + MOD) % MOD) #define inp(v) for(auto &a : v) cin >> a; #define out(v) for(auto &a : v) cout << a << " "; const int MOD = (int)1e9 + 7; const int MAX = (int)1e5 + 5; void solve() { //x >> y = x / (2 ^ y) //x << y = x * (2 ^ y) int n,cs,cf; cin >> n >> cs >> cf; vector<int> vt; for(int i = 1; i <= n; i++) { vt.pb(i); } int say = 0; int k = 0; if(n <= 11) { do{ bool ok = true; if(vt[0] != cs or vt[n - 1] != cf) { ok = false; } for(int i = 1; i < vt.size() - 1; i++) { if(!ok)break; if(vt[i] < vt[i + 1] and vt[i - 1] < vt[i]) { ok = false; break; } if(vt[i] > vt[i + 1] and vt[i - 1] > vt[i]) { ok = false; break; } } if(ok)say++; mod(say); }while(next_permutation(all(vt))); cout << say << endl; return; } do{ if(k >= 900000000)break; bool ok = true; if(vt[0] != cs or vt[n - 1] != cf) { ok = false; } for(int i = 1; i < vt.size() - 1; i++) { if(!ok)break; if(vt[i] < vt[i + 1] and vt[i - 1] < vt[i]) { ok = false; break; } if(vt[i] > vt[i + 1] and vt[i - 1] > vt[i]) { ok = false; break; } } if(ok)say++; mod(say); k++; }while(next_permutation(all(vt))); cout << say << endl; } signed main() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); int t = 1; //cin >> t; while (t--) { solve(); } }