#include <cstdio>
#include <cstdlib>
using namespace std;
/*
const int MAXN=1000;
int N;
int M[MAXN];
int ANS;

inline int Max(int a,int b)
{
	return a>b?a:b;
}

inline int Abs(int a)
{
	return a>0?a:-a;
}

inline int Compute()
{
	int Ans=0;
	int P=0;
	for(int i=1;i<=N;i++)
	{
		for(int j=1;j<=N;j++)
		{
			P++;
			if(i!=1) {Ans=Max(Ans,Abs(M[P]+M[P-N]));}
			if(i!=N) {Ans=Max(Ans,Abs(M[P]+M[P+N]));}
			if(j!=1) {Ans=Max(Ans,Abs(M[P]+M[P-1]));}
			if(j!=N) {Ans=Max(Ans,Abs(M[P]+M[P+1]));}
		}
	}
	return Ans;
}
*/
int main()
{
	freopen("coupons.in","r",stdin);
	freopen("coupons.out","w",stdout);
	int N;
	scanf("%d\n",&N);
	printf("%d\n",N*N+N/2+1);
	return 0;
}
	/*
	for(int i=1;i<=N;i++)
		for(int j=1;j<=N;j++)
			M[(i-1)*N+j]=(i-1)*N+j;
	ANS=Compute();
	int a,b,c,d;
	int K=N*N;
	int Q;
	for(int i=1;i<=20000000;i++)
	{
		srand(i);
		a=rand()%K+1;
		b=rand()%K+1;
		c=M[a],d=M[b];
		M[a]=d,M[b]=c;
		Q=Compute();
		if(Q<ANS)
			ANS=Q;
	}
	printf("%d\n",ANS);
	return 0;
}*/