#include <stdio.h>
main()
{
    float x=2.0,y=1.0,z=0.0,sum=0.0;
    int a;
    for(a=1;a<=20;a++)
    {    
        sum=sum+x/y;
        z=x;
        x=x+y;
        y=z;
    }
    printf("%f",sum);
    getchar();
 }