程序代码：

#include<stdio.h>
int main()
{
    int i=0;
    int a=0;
    int sum=0;
    int average=0;
    int stop=0;
    printf("请依次输入相加的数字然后单击一次回车键\n");
    printf("若输入结束，请输入数字-1\n"); 
    while(stop!=-1)
    {
        scanf("%d",&a);
        if(a==-1)
          {
              stop=a;
              printf("stop的值为%d\n",stop);
          }
        else
          {
              printf("stop的值为%d\n",stop);
            sum=sum+a;
            printf("+%d\n",a);
             printf("此时的和为%d\n",sum); 
            i=i+1;
            printf("已输入了%d位数\n",i);
             average=sum/i; 
          }
      
    }
    
    printf("平均值为%d",average);
    return 0;
}