/*

     模拟递推水题

 */

 #include <cstdio>

 #include <iostream>

 #include <cmath>

 #include <algorithm>

 #include <cstring>

 #include <string>

 #include <map>

 using namespace std;

 const int MAXN =  + ;

 const int INF = 0x3f3f3f3f;

 int a[MAXN][MAXN];

 int main(void)

 {

     #ifndef ONLINE_JUDGE

     freopen ("A.in", "r", stdin);

     #endif

     int n;

     while (~scanf ("%d", &n))

     {

         for (int i=; i<=n; ++i)

         {

             a[][i] = ;

             a[i][] = ;

         }

         for (int i=; i<=n; ++i)

         {

             for (int j=; j<=n; ++j)

             {

                 a[i][j] = a[i-][j] + a[i][j-];

             }

         }

         printf ("%d\n", a[n][n]);

     }

     return ;

 }