#include <iostream> #include <cstdio> #include <iomanip> #include <cmath> using namespace std; int main () { int k, sum, gold, days; cin >> k; for (int i=1; i<=k; i++) { if (i==1) { sum = 1; gold = 2; } else { days++; } sum = sum+gold; } cout << sum +1; return 0; }