输入10个学生的信息包括学号、姓名和成绩，输出学生的成绩等级和不合格学生人数。每个学生的记录均包含姓名、学号、成绩和等级，要求定义和调用函数.根据学生成绩确定其等级，并统计不合格人数，等级设置为：0~59为D，60~69为C，

70~84为B，85~100为A-Enter the 10 student information, including student number, name and achievements, the output level of student achievement and the number of students failed.

Each student s record contains the name, student number, grades and grade requirements definition and call the function set_grade (),

According to determine the level of student achievement, and the number of unqualified statistics, grade setting: 0 to 59 D, 60 ~ 69 for C,

70 to 84 B, 85 ~ 100 for A