#include <cstdio>

int main()
{
    int L;
    scanf("%d",&L);

    int bottles = L/7;
    if (L>=7 && L%7==3)
    {
        bottles++;
        printf("%d",bottles);
        return 0;
    }

    if (L>=7 && L%7==4)
    {
        bottles += 2;
        printf("%d",bottles);
        return 0;
    }

    L %= 7;
    bottles += L/5;
    L %= 5;
    bottles += L;
    printf("%d",bottles);
}