思路:有点像是斐波那契数列
#include <iostream>
#include <vector>
using namespace std;
int main() {
int n;
vector<int> num(56);
num[1] = 1;
num[2] = 2;
num[3] = 3;
num[4] = 4;
for (int i = 5; i < num.size(); i++) {
num[i] = num[i - 1] + num[i - 3];
}
while (cin >> n) {
if (n == 0)
break;
cout << num[n] << endl;
}
return 0;
}