1、编写程序,求 Sn=a+aa+aaa+...+aaaa...aaa（n个a）的值,其中a是一个数字,例如,a=2,n=5时,Sn=2+22

#include main(){int n;long a,sum = 0;printf("please input a and n,and press Enter to continue\n");scanf("%ld%d",&a,&n);//输入a和n的值while(n){sum += a;a += 10 * a;n--;}printf("sum = %ld\n",sum);}