1 #include <stdio.h>
 2 double f();
 3 int main(){
 4     printf("%.6f",f());
 5     return 0;
 6 }
 7 double f(){
 8     int a[24];
 9     a[0] = 1;
10     a[1] = 1;
11     int n = 24;
12     for (int i = 2; i < n ; i++){
13         a[i] = a[i-1] + a[i-2];
14     }
15     double result = 0.0;
16     for (int i = 0; i < 20; i++){
17         result += a[i+2] * 1.0 / a[i+1];
18     }
19     return result;
20 }