#include<stdio.h>
#include<math.h>
int mturns(int score)
{
    if (score<-1)
    {
        return -1;
    }
    int turns=0;
    int intscore=(int)ceil(score);
    while(intscore>0)
        if (intscore>=3)
        intscore -=3;
    
    else if(intscore==2)
    intscore -=2;
    else 
    intscore -=1;
    turns++;
}
int main ()
{
     int result =mturns(score);
     if  (result==-1)
     printf("Invalid Input");
     else
     printf("%d",result);
     return 0;
}