#include <stdlib.h>
#include <stdio.h>
 
typedef struct {
	unsigned char *bytes;
	unsigned int num_bytes;
} big_int;
 
void set_big_int(big_int *result, unsigned char number);
void multiply(big_int *result, unsigned char number);
void divide(big_int *result, unsigned char denominator);
unsigned char get_module(big_int *result, unsigned char denominator);
void factorial(big_int *result, unsigned char number);
int is_zero(big_int *big_integer);
 
int main() {
	big_int big_integer = {NULL, 0};
	unsigned char digit;
	unsigned int num_digits = 0;
	unsigned int result = 0;
 
	fprintf(stdout, "Adding all digits of 200!...\n");
 
	factorial(&big_integer, 200);
 
	while(is_zero(&big_integer) == 0) {
		num_digits++;
 
		digit = get_module(&big_integer, 10);
		fputc(digit + '0', stdout);
		result += digit;
 
		divide(&big_integer, 10);
	}
 
	fprintf(stdout, "\n\nDigit sum result: %u\n", result);
	fprintf(stdout, "Number of digits: %u", num_digits);
 
	fgetc(stdin);
	return 0;
}
 
void set_big_int(big_int *result, unsigned char number) {
	if(result->bytes != NULL)
		free(result->bytes);
 
	result->bytes = malloc(sizeof(unsigned char));
	result->bytes[0] = number;
	result->num_bytes = 1;
}
 
void multiply(big_int *result, unsigned char number) {
	register int i;
	unsigned int rest = 0;
 
	for(i = 0; i < result->num_bytes; i++) {
		rest = result->bytes[i] * number + rest;
		result->bytes[i] = rest & 0x000000FF;
		rest >>= 8;
 
		if(rest != 0 && i+1 == result->num_bytes) {
			result->num_bytes += 1;
			realloc(result->bytes, result->num_bytes);
			result->bytes[i+1] = 0;
		}
	}
}
 
void divide(big_int *result, unsigned char denominator) {
	register int i;
	unsigned int module = 0;
	unsigned int new_size = result->num_bytes;
 
	for(i = result->num_bytes-1; i >= 0; i--) {
		module = (unsigned int)result->bytes[i] + (module << 8);
		result->bytes[i] = module/denominator;
		module %= denominator;
	}
 
	for(i = result->num_bytes-1; i >= 0 && result->bytes[i] == 0; i--)
		new_size--;
 
	if(new_size != result->num_bytes) {
		result->num_bytes = new_size;
		realloc(result->bytes, new_size);
	}
}
 
unsigned char get_module(big_int *result, unsigned char denominator) {
	register int i;
	unsigned int module = 0;
 
	for(i = result->num_bytes-1; i >= 0; i--)
		module = ((unsigned int)result->bytes[i] + (module << 8))%denominator;
 
	return module;
}
 
void factorial(big_int *result, unsigned char number) {
	unsigned char i;
 
	set_big_int(result, 1);
	for(i = 2; i <= number; i++)
		multiply(result, i);
}
 
int is_zero(big_int *big_integer) {
	register unsigned int i;
	unsigned int result = 1;
 
	for(i = 0; result == 1 && i < big_integer->num_bytes; i++)
		result = big_integer->bytes[i] == 0;
 
	return result;
}

00000000000000000000000000000000000000000000000002747379830732698722222987169785
80071532604230714091306220668659755047521230423093757042424257723584928247221314
68192330452042466154126544229349889693732713367072758264311139928259426629160501
73624209724675203883691983121277140932648911048240302924330436994495344233524749
2362371786779531592260581239312363255305097463768756887

Digit sum result: 1404
Number of digits: 375