思路:
代码:
#include<bits/stdc++.h>
using namespace std;
int main(){
int a, b1, b2, month;
while(cin>>month){
a = 0;
b1 = 1;
b2 = 0;
int olda, oldb1, oldb2;
for (int i = 0; i < month-1; i++)
{
olda = a;
oldb1 = b1;
oldb2 = b2;
a = olda + oldb2;
b1 = olda + oldb2;
b2 = oldb1;
}
cout << a + b1 + b2 << endl;
}
return 0;
}