Accumulate_an

#include <iostream>

using namespace std;

int Solution1(int n, int a)
{
    // By ddl
    int sum = 0, k = a;
    for (int i = 0; i < n; i++) {
        sum += k;
        k = k * 10 + a;
    }

    return sum;
}

int Solution2(int n, int a)
{
    // By sjm
    int sum = 0, order = 1;

    for (int k = n; k > 0; k--) {
        sum += order * a * k;
        order *= 10;
    }

    return sum;
}

int main()
{
    int n = 5, a = 3;

    cout << Solution1(n, a) << endl;
    cout << Solution2(n, a) << endl;
}