求解...判断条件何来???

[java0000000]

/* Note:Your choice is C IDE */
/*鸡免同笼问题,输入所有鸡免的头数的脚数,求鸡免个数*/
#include "stdio.h"
main()
{
int f,h,c,r;
scanf("%d,%d",&f,&h);
if(f%2==0&&f>0&&f>2*h&&f<4*f)
{
r=(h-2*f)/2;
c=f-(h-2*f)/2;
printf("免为=%d",r);
printf("鸡为=%d",c);
}
else
{
printf("输入的数字不对");
}
}