#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ long long b=1,c=3,d,f; cin>>d; for(int i=3;i<=d;i++){ f=b; b+=c-f; c+=c-f+3; } cout<<c; return 0; }