int main(int argc, char*argv[])
{
    int m,d,y;
    sscanf("%d/%d/%d", &m, &d, &y);
    if (checkdate(m,d,y)) 
    {
        printf("valid\n");
    }
    else
    {
        printf("invalid\n");
    }
}
 
 
bool checkdate(int m, int d, int y)
{
  //gregorian dates started in 1582
  if (! (1582<= y )  )//comment these 2 lines out if it bothers you
     return false;
  if (! (1<= m && m<=12) )
     return false;
  if (! (1<= d && d<=31) )
     return false;
  if ( (d==31) && (m==2 || m==4 || m==6 || m==9 || m==11) )
     return false;
  if ( (d==30) && (m==2) )
     return false;
  if ( (m==2) && (d==29) && (y%4!=0) )
     return false;
  if ( (m==2) && (d==29) && (y%400==0) )
     return true;
  if ( (m==2) && (d==29) && (y%100==0) )
     return false;
  if ( (m==2) && (d==29) && (y%4==0)  )
     return true;
 
  return true;
}