哈哈又成功了

编写程序判断某年某月某日这一年中是第几天。

#include <iostream>
using namespace std;
int Sum(int,int,int);
int main()
{
 int y,m,t,sum;
 cout<<"请输入一个合法的日期：";
 cin>>y>>m>>t;
 sum=Sum(y,m,t);
 cout<<"是"<<y<<"年的第"<<sum<<"天"<<endl;
 return 0;
}
int Sum(int a,int b,int c)
{
 int s=c;
 if(a%400!=0&&b>0&&b<=12&&c>0&&c<=31)
  {
    for (;b>=1;)
         {   b=b-1;
             if(b==2)
             s=s+b*29;
             else if(b==1||b==3||b==5||b==7||b==8||b==10||b==12)
             s=s+b*31;
             else if(b==4||b==6||b==9||b==11)
             s=s+b*30;
             else s=s;
            return s;
        }
 }
 else if(b>0&&b<=12&&c>0&&c<=31)
          {      for(;b>=1;)
                  { b=b-1;
                    if(b=2)
                    s=s+b*28;
                    else if(b==1||b==3||b==5||b==7||b==8||b==10||b==12)
                              s=s+b*31;
                    else if(b==4||b==6||b==9||b==11)
                              s=s+b*30;
                    else s=s;
                    return s;
                  }
            } 
}