Codeforces 610A Pasha and Stick

/***
Md. Namzul Hasan
Shahjalal University of Science & Technology,Sylhet.
hasan08sust@gmail.com
***/

#include<bits/stdc++.h>
using namespace std ;
typedef long long ll ;
typedef int in ;
typedef unsigned long long ull ;
const double pi = 2*acos(0) ;
#define maxi 40000
#define pf printf
#define sc scanf
#define pb push_back
#define MEM(x,y) (memset((x),(y),sizeof(x)))
#define MIN(x,y) ((x) < (y) ? (x) : (y))
#define MAX(x,y) ((x) > (y) ? (x) : (y))
#define load(array,size)  for(int i=0 ; i<size ; i++) cin>>array[i]  ;
#define new_line  pf("\n")
#define clear_data(array) memset(array,0,sizeof(array))
#define highest_int 2147483647

int main()
{
    int n ;
    sc("%d",&n) ;

    if(n&1)
        pf("0") ;
    else
    {
        if(n%4==0)
        {
            pf("%d",(n/4)-1) ;
        }
        else
            pf("%d",n/4) ;
    }
    return 0;
}