백준 2839 c++

#include <iostream>

using namespace std;

int input(int lower, int upper);
int count_bag(int n);

int main(void)
{
	int N;
	N = input(3, 5000);
	cout << count_bag(N) << endl;

	return 0;
}

int input(int lower, int upper)
{
	int A;

	while (1)
	{
		cin >> A;
		if (A >= lower && A <= upper)
		{
			break;
		}
		else
		{
			;
		}
	}

	return A;
}

int count_bag(int n)
{
	int i, j;
	int bag_3 = n / 3, bag_5 = n / 5;
	int count = bag_3 + bag_5;

	for (i = 0; i <= bag_3; i++)
	{
		for (j = 0; j <= bag_5; j++)
		{
			if (i * 3 + j * 5 == n)
			{
				if (i + j < count)
				{
					count = i + j;
				}
				else
				{
					;
				}
			}
			else
			{
				;
			}
		}
	}
	if(count != bag_3 + bag_5 || n == 3)
	{
		;
	}
	else
	{
		count = -1;
	}

	return count;
}