SOLUTION OF URI 1156

//  1156   (Mahmud_Jamil) BRUR
//   S Sequence II





#include <stdio.h>
int main()
{
    double a,b=1,c, S=0;
    for(a=1; a<=39; a+=2)
    {
        c=a/b;
        S+=c;
        b*=2;
    }
    printf("%.2lf\n",S);
    return 0;
}