How to find first digit of user input w/o loops

Question

I've been trying to find the first digit of the user input without using loops. I did try to apply methods here ( https://codeforwin.org/2015/06/how-to-find-first-and-last-digit-of-any-number.html ) but it seems like I am getting core dumped error before entering the second function. Below is my code. Any help would be greatly appreciated...

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

void takeInput (int *input);
void firstDigit (int *input, int *digit1);

int main (void)
{
//local declarations
int input; //user input, number from -99999 to 99999
int digit1;
int digit2;
int digit3;
int digit4;
int digit5;
takeInput (&input);
firstDigit (&input, &digit1);
return 0;
}

void takeInput (int *input)
{
printf("type input in -> ");
scanf("%d", input);
return;
}

void firstDigit (int *input, int *digit1)
{
int temp;
printf("firstDigit ");
temp = *input % 10000;
digit1 = *input - temp;
*input = *input % 10000;
//  printf("%d", *input);
//  temp = (int) log10(*input);
//  digit1 = (int) (*input / pow(10, temp));
printf("%d", *digit1);
return;
}

Answer 1

you can convert it to string and then finding first and last digit.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
    char string[20];
    int input;
    scanf("%d", &input);
    itoa(input, string, 10);
    printf("first digit: %d\n", string[0] - '0');
    printf("last digit: %d\n", string[strlen(string) - 1] - '0');


    return 0;
}