栈题解

#include <bits/stdc++.h>
using namespace std;
int n,f[30];
int main(){
	cin >> n;
	f[0] = 1, f[1] = 1;
	for(int i = 2; i <= n; i ++)
		for(int j = 0; j < i; j ++)
			f[i] += f[j] * f[i - j - 1];
	cout << f[n] << endl;
    return 0;
}