如何编写程序，求Sn=a+aa+aaa+aaaa+aaaaa…的前n项之和？

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求Sn=a+aa+aaa+aaaa+aaaaa…的前n项之和

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#include 
#include 

int main()
{
    int a = 0;
    int n = 0;
    int i = 0;
    int an = 0;
    int Sn = 0;
    scanf("%d%d", &a, &n);
    for (i=0; i10 * an + a;
        Sn += an;
    }
    printf("%d\n", Sn);
    return 0;
}

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程序运行结果如下：

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