#include<stdio.h>
#include<math.h>
int main()
{
double eps;
scanf("%lf",&eps);
double s=0.0,k=1.0,item=0.0;
int mu=1;
while(s<=eps)
{
s+=k*(1.0/mu);
k=-k;
mu+=3;
}
printf("sum = %lf",s);
}
#include<stdio.h>
#include<math.h>
int main()
{
double eps;
scanf("%lf",&eps);
double s=0.0,k=1.0,item=0.0;
int mu=1;
while(s<=eps)
{
s+=k*(1.0/mu);
k=-k;
mu+=3;
}
printf("sum = %lf",s);
}