有规律的。找到就ok
#include<stdio.h>
int main() {
int n;
while(scanf("%d",&n)!=EOF) {
int x;
if(n%2!=0)
printf("0\n");
else
{
if(n%4==0)
printf("%d\n",n/4-1);
else
printf("%d\n",n/4);
}
}
return 0;
}