输入百分制成绩，并把它转换成五级分制，转换公式为：

#include<iostream>
using namespace std;
int main()
{
double score; char grade;
   cout << "score=";
      cin >> score;
   if ( score >= 0 && score <= 100 )
{
switch  ( int( score ) /10 )
{
case   10:
  case   9:  grade = 'a'; break;
  case   8:  grade = 'b'; break;
  case   7:  grade = 'c'; break;
  case   6:  grade = 'd'; break;
  case   5:  
  case   4:  
  case   3:  
  case   2:  
  case   1:  
  case   0:  grade = 'e'; break;
}
 }
      else
       {
cout <<"数据输入错误！"<< endl;
         goto end;
}
         cout << grade << endl;
end:  ;                      //分号不能省
}