codeforces problem solution in c

even_palindrome.c

// my solution to problem http://codeforces.com/problemset/problem/897/B
#include<stdio.h>
#include<math.h>

int main(){

int num_digit = 0, remainder = 0;
long int num_palindrome, count = 0, n = 0;
long long int palindrome = 0, mod = 0, rev_num = 0, arr_sum = 0;

scanf("%ld  %lld", &num_palindrome, &mod);

    while(num_palindrome > count){

        count++;
        remainder = 0;
        rev_num = 0;
        num_digit = 0;

        n = count;
        while(n != 0){
            n /= 10;
            num_digit++;
        }

        n = count;
        while(n != 0){
            remainder = n % 10;
            rev_num = rev_num * 10 + remainder;
            n /= 10;
        }

        palindrome = count * (int)pow(10, num_digit) + rev_num;
        //printf("%lld", palindrome);
        //printf(" count: %ld\n", count);

        arr_sum +=palindrome;
    }//end of while loop


    printf("%lld", (arr_sum % mod));

}