#include<fstream.h>
#include<stdlib.h>
long long a[100],b[100],suma;
int i,j,q,n;
int main()
{
ifstream in("nunta.in");
ofstream out("nunta.out");
in>>n;
q=n/2;
for (i=1; i<=n-1; i++)
	{
	b[i]=1;
	b[0]=1;
	for (j=1; j<=i-1; j++)
		b[j]=a[j-1]+a[j];
        if (i>=n-n/2) {suma+=b[q];q--;}
	memmove(a,b,(n)*sizeof(long long));
	}
cout<<suma+1;
in.close();
out.close();
return 0;
}