#include <stdio.h>
int main()//求平均值

{
int a[10] = { 1,2,3,4,5,6,7,8,9,21 };
float b = 0;
int i = 0;
while (i < 10)
{
b = a[i] + b;
i++;
}
printf("%f\n", b/10);

return 0;
}