动态规划

#include <iostream>

using namespace std;

typedef long long LL;

const int N = 1010, MOD = 1e9 + 7;

int n;
int f[N];

int main()
{
    cin >> n;

    f[0] = 1;
    for (int i = 1; i <= n; i ++ )
        for (int j = 0; j < i; j ++ )
            f[i] = (f[i] + (LL)f[j] * f[i - 1 - j]) % MOD;

    cout << f[n] << endl;

    return 0;
}