题解 | #不死神兔问题#

#include <iostream>
using namespace std;

int getSum(int n);

int main() {

    int n;
    cin >> n;

    cout << getSum(n) << endl;

    return 0;
}

int getSum(int n) {

    // write your code here......
    if(n <= 2) return 1;
    if(n == 3) return 2;
    return getSum(n - 1) + getSum(n - 1) - getSum(n - 3); 
}