#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>

char* ecvt(double x, int n, int* dp, int* sign) {
  static char buf[16];
  char tmp[32];
  int i, j;

  if (n - 1U > 15)
    n = 15;
  sprintf(tmp, "%.*e", n - 1, x);
  i = *sign = (tmp[0] == '-');
  for (j = 0; tmp[i] != 'e'; j += (tmp[i++] != '.'))
    buf[j] = tmp[i];
  buf[j] = 0;
  *dp = atoi(tmp + i + 1) + 1;

  return buf;
}