#include <stdio.h>

int main() {
    double total=0.0;
    double input=0.0;
    int num=0;

    for( ; input>=0.0 ; )
    {
        total+=input;
        printf("실수 입력(minus to quit) : ");
        scanf("%lf", &input);
        num++; // 1 2 3
    }
    printf("평균: %f \n", total/(num-1));
    return 0;
}