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

int main ( );
float f ( float x );

int main ( )
{
  float a;
  char answer;
  float b;
  float c;
  char cr;
  float fa;
  float fb;
  float fc;

  a = 0.0;
  fa = f ( a );
  b = 7.0;
  fb = f ( b );

  while ( 1 )
  {
    c = ( a + b ) / 2.0;
    fc = f(c);

    printf ( "\n" );
    printf ( "Left : f(%g) = %g, f(%g) = %g\n", a, fa, c, fc );
    printf ( "Right: f(%g) = %g, f(%g) = %g\n", c, fc, b, fb );
    printf ( "L: keep left, R: keep right, Q: quit\n" );

    scanf ( "%c%c", &answer, &cr );

    if ( answer == 'L' || answer == 'l' )
    {
      b = c;
      fb = fc;
    } 
    else if ( answer == 'R' || answer == 'r' )
    {
      a = c;
      fa = fc;
    }
    else
    {
      printf ( "We will stop now.\n" );
      break;
    }
  }

  return 0;
}


float f ( float x )
{
  float value;

  value = cos ( x ) - x;

  return value;
}