这个程序中天数定义

#include <stdio.h>

int main() 

{ 

    int sum; //这里改成int sum;  结果就出错了 求解??????

int month=8;

    switch(month)

    {

case 12:sum+=30;

case 11:sum+=31;

case 10:sum+=30;

case 9:sum+=31;

case 8:sum+=31;

case 7:sum+=30;

case 6:sum+=31;

case 5:sum+=30;

case 4:sum+=31;

break;

}

printf("%d\n",sum);

return 0;

}