#include<stdio.h>
#define NMAX 1001
unsigned long c[NMAX][NMAX];
int n;
int main()
{
int i,j;
unsigned long s=0;
freopen("nunta.in","r",stdin);
freopen("nunta.out","w",stdout);
scanf("%d",&n);
c[1][1]=c[1][2]=1;
for(i=2;i<=n;i++)
	for(j=1;j<=i+1;j++)
		c[i][j]=c[i-1][j-1]+c[i-1][j];
/*	for(i=2;i<=n;i++)

	{ printf("%d",i);for(j=1;j<=i+1;j++)
			printf("%2ld ",c[i][j]);
		printf("\n");
}*/
for(i=n;i>=(n+1)/2;i--)
	s+=c[i][n-i+1];
printf("%ld",s);
	return 0;
}