怎么做第2道题？不会写程序😭

//知识有限，仅供参考
#include<stdio.h>
int main(void)
{
int a[5]={0},b;
unsigned int number;
printf("Please input a number:");
scanf_s("%5d",&number);
a[0]=number/10000;
a[1]=(number-a[0]*10000)/1000;
a[2]=((number-a[0]*10000)-a[1]*1000)/100;
a[3]=(number-(a[0]*100+a[1]*10+a[2])*100)/10;
a[4]=number%10;
b=a[0]+a[1]+a[2]+a[3]+a[4];
printf("%d",b);
return 0;
}