输入a和n，计算a+aa+aaa+.....+aa...aa(n个a)

#include#include#includeint Na(int a,int n){ if(n==1)return a;else return a*pow(10,n-1)+Na(a,n-1);}int Sum(int a,int n){int sum=0; for(int i=n;i>=1;i--) { sum += Na(a,i); } return sum;}void main(){ long start,end;start=clock();printf("请输入a和n的值：");int a,n;scanf("%d%d",&a,&n);printf("%d\n",Sum(a,n)%1000000007);end=clock();printf("运行时间为：%lfms",end-start);}