백준 2839: 설탕배달

b_2839.cpp

#include <iostream>

int return_sum(int three_count, int five_count) {
    return three_count * 3 + five_count * 5;
}


int main(void) {
    int num;
    std::cin >> num;
    
    for(int i = num / 5; i >= 0; i--) {
        int three_num = 0;
        while(true){
            int sum = return_sum(three_num, i);
            if(sum < num) {
                three_num++;
                continue;
            }
            if(sum == num) {
                std::cout << three_num + i << std::endl;
                i = -1;
                break;
            }
            if(sum > num){
                break;
            }
        }
        if(i == 0) {
            std::cout << -1 << std::endl;
        }
    }
}