客似云来

题目：https://www.nowcoder.com/pat/2/problem/252
 1 #include <iostream>
 2 #include <algorithm>
 3 using namespace std;
 4 const int maxn = 80 + 1;
 5 long long f[maxn];
 6 
 7 void db(){
 8     f[1] = 1;
 9     f[2] = 1;
10     for (int i = 3; i < maxn; i++){
11         f[i] = f[i - 1] + f[i - 2];
12     }
13     
14 }
15 
16 int main(){
17     std::ios::sync_with_stdio(false);
18     int from, to;
19     db();
20     while (cin >> from >> to){
21         long long ans = 0;
22         for (int i = from; i <= to; i++){
23             ans += f[i];
24         }
25         cout << ans << endl;
26     }
27     //system("pause");
28     return 0;
29 }