#include <stdio.h>

int main() {
    float grade, sum;
    int	  gradeCount;
    int   another;
    do {
	sum = gradeCount = 0;
	printf("Enter grade: ");
	scanf("%g", &grade);
	while (grade >= 0.0) {
	    sum += grade;
	    ++gradeCount;
	    printf("Enter grade: ");
	    scanf("%g", &grade);
	}
	printf("Average: %g\n\n",
	       sum/gradeCount);
	printf("Another class: ");
	scanf("%d", &another);
    } while (another != 0);

    return 0;
}