#include <math.h>
#include <float.h>

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double fdiml(long double x, long double y) {
  return fdim(x, y);
}
#else
long double fdiml(long double x, long double y) {
  if (isnan(x))
    return x;
  if (isnan(y))
    return y;
  return x > y ? x - y : 0;
}
#endif