你说它有什么功能呢

#include<iostream>
using namespace std;
int a[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
int main()
{
 int n;
 while(cin>>n)
 {
         int i,j,k,jj;
        int b[8]={0,0,0,0,0,0,0};
  for(i=1900;i<1900+n;i++)
  {
   if((i%4==0&&i%100!=0)||i%400==0)
    a[2]=29;
   for(k=1;k<=12;k++)
   {
    for(j;j+7<=a[k];)
     j+=7;
                 jj=a[k]-j;
     switch (jj+1)
     {
     case 1:b[6]++;break;
                 case 2:b[7]++;break;
                 case 3:b[1]++;break;
                 case 4:b[2]++;break;
     case 5:b[3]++;break;
                 case 6:b[4]++;break;
                 case 7:b[5]++;break;
     default:b[0]++;break;
     }
     j=7-jj;
   }
  }
  for(i=1;i<=7;i++)
   cout<<b[i]<<" ";
 }
return 0;
}