#include <stdio.h>

#include <string.h>

#include <ctype.h>

#include <errno.h>

#include <limits.h>



long strtol(const char *s, char *endptr, int base)

{

  int power;

  int sign = 1;

  const char *ptr = s;

  long result = 0;

  /*check the base*/

  if ((base<2 || base >36) && base!=0)

  {

    errno=EINVAL;

    return 0;

  }

  if(*ptr == '\n')

    return 0;

  /*delating spaces and tabulations at the begining*/

  while(isspace(ptr))

    ptr++;

  if(!ptr) return 0;

  /*case: base =0, string starts with '0x' or '0X' (16) or '0' (8) or it's (10)*/

  if(base == 0)

  {

    if(*ptr == '0' && (*ptr+1 == 'x' || *ptr+1 == 'X'))

      base = 16;

    else

      if(*ptr == '0')

            base = 8;

      else

            base=10;

  }

  if(*ptr=='+')

    ptr = ptr+1;

  else

    if(*ptr == '-')

    {

      sign = -1;

      ptr = ptr+1;

    }

  /*case: base = 16, string starts with '0x' or '0X'*/

  if(base == 16 && (*ptr == '0' && (*(ptr+1)== 'x' || *(ptr+1)== 'X')))

    ptr = ptr+2;

  /*case: base = 8, string starts with 0*/

  if(base == 8 && *ptr == '0')

    ptr = ptr+1;

  /*remove zeros at the begining*/

  while(*ptr == '0') ptr++;

  if(!ptr)

  {

    return 0;

  }

  /*set end pointer*/

  for(*endptr = ptr; endptr < (ptr +strlen(ptr)-1); endptr++)

    if(converter(*endptr)>(base-1) || converter(*endptr)==-1)

      break;

  power = 1;

  for(endptr-=1; endptr>=ptr; endptr--)

  {

    result += converter(*endptr) * power;

    power *=base;

  }

  if(result*sign> LONG_MAX)

  {

    errno = ERANGE;

    return LONG_MAX;

  }

  if(result*sign<LONG_MIN)

  {

    errno = ERANGE;

    return LONG_MIN;

  }

  return result*sign;



}

/**       function converting letters and numbers (char type) to numbers(int type)

*          @param sth the character

*/

int converter(char sth)

{

  if(sth>='0' && sth<='9') return sth - '0';

  if(sth>='a' && sth<='z') return sth - 'a' + 10;

  if(sth>='A' && sth>='Z') return sth-'A' + 10;

  return -1;

}