求Sn=a+aa+aaa+...+aa...a的值

#include<cstdio>#include<algorithm>#include<iostream>#include<cmath>#include<iomanip>#include<cstring>using namespace std;int main(){    int a,n,s=0,sum=0;    cin >> a >> n;    for(int i=1; i<=n; i++){        s+=a;        a=a*10;        sum+=s;    }    cout << sum << endl;    return 0;}