#include <bits/stdc++.h> using namespace std; long long jiecheng(long long jc) { if (jc == 1) return 1; return jiecheng(jc-1) * jc; } long long CTLS(long long n) { if (n<=2) return 0; // int h = n-1; return jiecheng(2*n)/jiecheng(n+1)/jiecheng(n); } int main() { long long n, ans = 0; cin >> n; cout << CTLS(n-2); return 0; }