설탕 배달 (그냥 구현)

https://www.acmicpc.net/problem/2839

2839번: 설탕 배달

#include <iostream>

using namespace std;

int main()
{
    int N;
    cin >> N;

    int num5 = N/5;
    int num3 = 0;
    while(true)
    {
        int leftN = N - 5*num5;
        if(leftN%3 == 0)
        {
            num3 = leftN/3;

            cout << num3 + num5;
            return 0;
        }

        if(num5>=1)
        {
            num5--;
        }
        else 
        {
            cout << "-1";
            return 0;
        }
    }

    cout << "-1";
    return 0;
}