#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
  
long double f( long double x, long double  k )
{
   return expl( x ) - k;
}
  
int main(int argc, char **argv)
{
   long double x;
   long double k;
   long double lnx;
   long double y;
   char pszString[256] = "2";
  
   if ( argc < 2 )
   {
      printf( "Enter a number to find exponential of:" );
      fgets( pszString, sizeof( pszString ), stdin );
      puts( pszString );
   }
   else
      strncpy( pszString, argv[1], sizeof( pszString ) );
  
   k = atof( pszString );
   x = expl( k ) * 1.00001; /* form estimate correct to 5 digits */
   lnx = logl(x);
   printf("answer = %30.20LeL\nx = %30.20LeL\n", expl( k ), x - x*lnx + x*k );
  
   y = lnx - k;
   x -= 3. * x * ( 2 + 3 * y + 2 * y * y ) * y /
   ( 6 + 12 * y + 11 * y * y + 6 * y * y * y );
   printf("answer = %30.20LeL\nx = %30.20LeL\n", expl( k ), x );
   return 0;
}