#include <stdio.h>


float abs(float x) {
   return x < 0 ? -x : x;
}

float fib(int n) {
   if (n == 1 || n == 2) {
      return 1.0;
   }
   return fib(n - 1) + fib(n - 2);
}

float phi(float f) {
   float phi_1;
   float phi_2;

   int i;
   for (i = 3;;++i) {
      phi_1 = fib(i)      / fib(i + 1);
      phi_2 = fib(i + 1) / fib (i + 2);

      if (abs(phi_2 - phi_1) < f) {
         return phi_2;
      }
   }
}

int main(void) {

   printf("%f\n", phi(0.0001));
   return 0;
}