#include <iostream>
#include <cstring>
using namespace std;

long long f[25][25];

int main(){
	int n;
	while (cin>>n){
		memset(f,0,sizeof(f));
		for (int i=1;i<=n;i++)
			f[i][0]=1;
        for (int i=1;i<=n;i++){
			for (int j=1;j<=i-1;j++)
				f[i][j]=f[i-1][j]+f[i][j-1];
			f[i][i]=f[i][i-1];
		}
		cout<<f[n][n]<<endl;
	}
	return 0;
}
/**************************************************************
	Problem: 2120
	User: admin
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2076 kb
****************************************************************/