int main() {
	int n;
	printf("nhap vao 1 so nguyen duong");
	scanf_s("%d", &n);
	int tong = 0;
	while (n > 0) {
		tong += n % 10;
		n = n / 10;
	}
	printf("tong cac chu so trong n la: %d", tong);
	return 0;
}