/* Solution with switch_case instruction */

/*Given grades of 4 tests. Get A if average is 90 or above*/
/*B if average is 80-89, C if average is 70-79, D if average is 60-69*/
/*F if average is lower than 60*/


#include <stdio.h>

float test1, test2, test3, test4; 
float average;
int grade_range;
char grade;

void main() {
  scanf ("%f%f%f%f", &test1, &test2, &test3, &test4);
  average = (test1+test2+test3+test4)/4;

/* since I cannot use float as switch expression, I define integer ranges */

  if (average>=90.0)
    grade_range = 1;
  else if (average>=80.0)
    grade_range = 2;
  else if (average>=70.0)
    grade_range = 3;
  else if (average>=60.0)
    grade_range = 4;
  else
    grade_range = 5;
 

  switch (grade_range) {
  case 1: grade = 'A'; break;
  case 2: grade = 'B'; break;
  case 3: grade = 'C'; break;
  case 4: grade = 'D'; break;
  default : grade = 'F';
  }
  printf ("%c\n", grade);
}