卡特兰数的应用

#include<cstdio>#include<cstring>#include<iostream>#define ll long long#define mod 1000000007using namespace std;ll a[10000+10];int main(){    int n;    int i,j;    a[0]=1;    for(i=1;i<=10000;i++)    {       for(j=0;j<i;j++)       {           a[i]=(a[j]*a[i-1-j]%mod+a[i])%mod;       }    }    while(cin>>n)    {        cout<<a[n]<<endl;    }    return 0;}