Division of large numbers in c

#include<stdio.h>

#include<math.h>

#include<stdlib.h>

#include<string.h>

#define MAX 10000

char * division(char [],unsigned long);

int main(){

    char a[MAX];

    unsigned long b;

    char *c;

    printf("Enter the divdend : ");

    scanf("%s",a);

    printf("Enter the divisor : ");

    scanf("%lu",&b);

    c = division(a,b);

    printf("\nQuotient of the division : ");

    printf("%s",c);

    return 0;

}

char * division(char a[],unsigned long b){

    static char c[MAX];

    int la;

    int i,k=0,flag=0;

    unsigned long temp=1,reminder;

    la=strlen(a);

    for(i=0;i<=la;i++){

         a[i] = a[i] - 48;

    }

    temp = a[0];

    reminder = a[0];

    for(i=1;i<=la;i++){

         if(b<=temp){

             c[k++] = temp/b;

             temp = temp % b;

             reminder = temp;

             temp =temp*10 + a[i];

             flag=1;

         }

         else{

             reminder = temp;

             temp =temp*10 + a[i];

             if(flag==1)

                 c[k++] = 0;

         }

    }

    for(i=0;i<k;i++){

         c[i]=c[i]+48;

    }

    c[i]= '\0';

    printf("Reminder of division:  %lu  ",reminder);

    return c;

}