Problema con while en C

Hola estoy empezando a programar en C y estoy con un ejercicio de calculo de promedio de unas calificaciones con while que a mi entender deberia funcionar pero no lo hace! Aqui esta mi codigo

Código:

//3.8 CLASS AVERAGE PROGRAM WITH SENTINEL CONTROLLED REPETITION
#include <stdio.h>

int main (void)
{
    int counter;//number of grades entered
    int grade;//grades value
    int total;//sum of grades
    float average;//average

    //initialization phase
    total = 0;
    counter = 0;
    grade = 0;

    //processing phase
    while( grade != -1) {
        puts( "Please type the grade and press enter. To finish type \"-1\"." );//asks user to type a grade
        scanf( "%d", &grade );//stores the grade typed by the user into the grade variable
        total = total + grade;//adds the grade typed by the user to the total
        counter = counter + 1;//adds one to the counter
    }//end while

    //termination phase
    //if counter is not equal to zero, calculate the average and print it, if not print "No grades were entered"
    if( counter != 0){
        average = ( float ) total / counter;
        printf( "Average is %.2f\n", average );
    }//end if
    else{
        puts( "No grades were entered" );
    }//end else
}//end main

y aqui esta el codigo que funciona, pero me gustaría entender por que el mio no lo hace:

Código:

//3.8 CLASS AVERAGE PROGRAM WITH SENTINEL CONTROLLED REPETITION
#include <stdio.h>

int main (void)
{
    int counter;//number of grades entered
    int grade;//grades value
    int total;//sum of grades
    float average;//average

    //initialization phase
    total = 0;
    counter = 0;

    //processing phase
        puts( "Please type the grade and press enter. To finish type \"-1\"." );//asks user to type a grade
        scanf( "%d", &grade );//stores the grade typed by the user into the grade variable

    while( grade != -1) {
        total = total + grade;//adds the grade typed by the user to the total
        counter = counter + 1;//adds one to the counter
        puts( "Please type the grade and press enter. To finish type \"-1\"." );//asks user to type a grade
        scanf( "%d", &grade );//stores the grade typed by the user into the grade variable

    }//end while

    //termination phase
    //if counter is not equal to zero, calculate the average and print it, if not print "No grades were entered"
    if( counter != 0){
        average = ( float ) total / counter;
        printf( "Average is %.2f\n", average );
    }//end if
    else{
        puts( "No grades were entered" );
    }//end else
}//end main

Desde ya MUCHAS GRACIAS!

while( grade != -1){ /* 4 */
puts( "Please type the grade and press enter. To finish type \"-1\"." );
scanf( "%d", &grade ); /* 1 */
total = total + grade; /* 2 */
counter = counter + 1; /* 3 */
}