#include<fstream.h>

int i,j,n;
long long s,a[100][100];

int main()
{
 ifstream f("nunta.in");
 ofstream g("nunta.out");
 f>>n;
 for(i=1;i<n+1;i++)
  for (j=0;j<i+1; j++)
   if (j==0) a[i][j]=1; else
   if (i==j) a[i][j]=1; else
    a[i][j]=a[i-1][j-1]+a[i-1][j];
s=1;
 for(i=1; i<n/2+1;i++)
  s=s+a[n-i][i];
g<<s<<"\n";
g.close();

return 0;
}