#include <bits/stdc++.h>
using namespace std;
int a[105][105];
int f(int x, int y)
{
	if (a[x][y] == 1)
	{
		return a[x][y];
	}
	if (y == 0)
	{
		return a[x][y] = 1;
	}
	if (x == 0 && y == 1)
	{
		return  a[x][y] = 1;
	}
	if (x == 0)
	{
		x++;
		y--;
	}
	return a[x][y] = f(x - 1 , y) + f(x + 1, y - 1);
}
int main()
{
	int n;
	cin >> n;
	cout << f(1, n - 1) << endl; 
	return 0;
}