这个程序哪里有错误啊？我怎么找不出来啊

#include<stdio.h>

#define P printf

void main()

{

int rn(int leap,int n);

int n,y,r,num,leap;

scanf("%d%d%d",&n,&y,&r);//输入年月日

leap=rn(leap,n); //判断是否是闰年

switch(y)

{

case 1:num=r;

case 2:num=31+r;

case 3:if(leap)num=31+28+r;

else num=31+29+r;

case 4:if(leap)num=31+28+31+r;

else num=31+29+31+r;

case 5:if(leap)num=31+28+31+30+r;

else num=31+29+31+30+r ;

case 6:if(leap)num=31+28+31+30+31+r;

else num=31+29+31+30+31+r;

case 7:if(leap)num=31+28+31+30+31+30+r;

else num=31+29+31+30+31+30+r;

case 8:if(leap)num=31+28+31+30+31+30+31+r;

else num=31+29+31+30+31+30+31+r;

case 9: if(leap)num=31+28+31+30+31+30+31+31+r;

else num=31+29+31+30+31+30+31+31+r;

case 10:if(leap)num=31+28+31+30+31+30+31+31+30+r;

else num=31+29+31+30+31+31+30+31+30+r;

case 11:if(leap)num=31+28+31+30+31+30+31+31+30+31+r;

else num=31+29+31+30+31+30+31+31+30+31+r;

case 12:if(leap)num=31+28+31+30+31+30+31+31+30+31+30+r;

else num=31+29+31+30+31+30+31+31+30+31+30+r;

};

P("%d\n",num);

int rn(int leap,int n) //闰年判断函数

{

if(n%4==0||n%100==0&&n%400==0)

leap=1;

else

leap=0;

rerurn leap;

}

}

我刚学C语言请多多指教！

break;