#include <stdio.h>
#include <math.h>

double inp()
{
    double ac;
    printf("Input accuracy\n");
    while(scanf("%lf", &ac) != 1)
    {
        while(getchar() != '\n');
        printf("ERROR\n");
    }
        return ac;
}
int fib(int n)
{
    int i;
    int f1=0;
    int f2=1;
    int f3=1;

    for (i=3; i<=n+1; i++)
    {
        f3= f1+f2;
        f1= f2;
        f2= f3;
    }
    return (f3);
}
double result(double ac)
{
    int i=1;
    double r;
    int fib1, fib2, fib3;
    do
    {
        fib1=fib(i);
        fib2=fib(i+1);
        fib3=fib(i+2);
        r=fabs(((double)fib3/(double)fib2)-((double)fib2/(double)fib1));
        i++;
    }
    while(r>ac);
    return ((double)fib3/(double)fib2);
}

main(void)
{
    double ac;
    ac=inp();
    printf("%.7lf\n", result(ac));
}