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

void unlockInput()
{
   const char endOfInputCharacter = '\n';
   char currentCharOnInput = 0;

   while (endOfInputCharacter != currentCharOnInput)
   {
      currentCharOnInput = getchar();
   }
}

double readDouble(const char* askString, const char* onWrongInputString)
{
   double returnValue;
   const int successCode = 1;
   int inputOperationCode;

   bool isInputCorrect = false;
   while (false == isInputCorrect)
   {
      printf("%s", askString);
      inputOperationCode = scanf("%lf", &returnValue);
      unlockInput();

      if (successCode == inputOperationCode)
      {
         isInputCorrect = true;
      }
      else
      {
         printf("Input Error: %s\n", onWrongInputString);
      }
   }

   return returnValue;
}

double calculate(const double s)
{
   const double xInDegees = 60.0;
   const double xInRadian = xInDegees * M_PI / 180.0;
   const double x = tan(xInRadian);
   const double firstBrackets = pow((pow(cos(x), 2) - log(x + 1)), 3);
   const double secondBrackets = fabs(x - s * log(pow(x, 2) - 1));

   const double y = firstBrackets - secondBrackets * 1.5 * pow(10, -3);

   return y;
}

int main()
{
   double numberSvalue;
   double numberYvalue;

   numberSvalue = readDouble("Enter S value: ", "Wrong value. Please, enter number again.");

   numberYvalue = calculate(numberSvalue);

   printf("Result is: %lf\n", numberYvalue);

   return 0;
}