贪心,能凑够5瓶就先凑,再凑3瓶的
#include <iostream>
using namespace std;
int main()
{
int n ;
cin >> n;
int cnt = n / 10;
int t = cnt;
if(cnt >= 5) cnt += t / 5 * 2, t %= 5;
if(t >= 3) cnt += t / 3;
cout << cnt <<endl;
return 0;
}