阶乘

#include <iostream>
using namespace std;
int a(int n){
    if(n<=2){
        return 1;
    }
    return a(n-1)+a(n-2);//a（n-1）*n
}
int main(int argc, char** argv) {
    system("pause");
    int N;
    cin>>N;
    cout<<a(N)<<endl;
    return 0;
}