#include <stdio.h>

int main()
{
    float grade, sum = 0.0;
    int 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",
	sum/gradeCount);

    return 0;
}