#include using namespace std; #define F first #define S second #define R cin>> #define Z class #define ll long long #define ln cout<<'\n' #define in(a) insert(a) #define pb(a) push_back(a) #define pd(a) printf("%.10f\n",a) #define mem(a) memset(a,0,sizeof(a)) #define all(c) (c).begin(),(c).end() #define iter(c) __typeof((c).begin()) #define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--) #define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++) #define rep(i,n) REP(i,0,n) #define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++) templatevoid pr(A a){cout<void pr(A a,B b){cout<void pr(A a,B b,C c){cout<void pr(A a,B b,C c,D d){cout<void PR(A a,ll n){rep(i,n){if(i)cout<<' ';cout<=0&&x=0&&y P; void Main() { ll n; R n; if(n==1) { pr(0); return; } ll a[n],l=0,r=n-2; rep(i,n/2) { if(i%2==0) { a[l]=i+1; l+=2; } else { a[r]=i+1; r-=2; } } l=1,r=n-1; rep(i,n/2+n%2) { if(i%2==0) { a[r]=n-i; r-=2; } else { a[l]=n-i; l+=2; } } ll ans=0; rep(i,n) ans+=a[i]*a[(i+1)%n]; pr(ans); /* ll l=1,r=n,ans=0; rep(i,n) { if(l==r) break; pr(l,r,l*r); ans+=l*r; if(i%2) r--; else l++; } pr(ans+r); */ } int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}