#include <stdio.h>
#define max(x,y) (x>y?x:y)
struct BI{
	char x[43],n;
	void operator+=(BI &a)
	{
		char mx=max(n,a.n),k=0;
		for(char i=1;i<=mx||k;i++)
		{
			if(i>n)x[i]=0;
			x[i]+=a.x[i]+k;
			k=x[i]/10,x[i]%=10;
			n=max(n,i);
		}
	}
	void operator=(char a){n=1,x[1]=a;}
	void out(){for(char i=n;i>=1;i--)printf("%d",x[i]);}
};
BI f,g,f1,f2,g1,g2;
int main()
{
	char n;
	scanf("%d",&n);
	f=1,f1=1,f2=1,g1=0,g2=0;
	for(char i=1;i<=n;i++)
	{
		if(i)g2+=f,g2+=f;
		if(i<n)g1+=g2;
		if(i<n)g+=g1;
		f=f1;
		f2+=f;
		f1+=f2;
	}
	g+=f;
	g.out();
	return 0;
}