50分求助，困惑了好久的题目

#include<iostream>
using namespace std;
int main()
{
    char ch[15];
    int num = 1,ans=0;
    for (int i = 1; i <= 12; i++)
    {
        cin >> ch[i];
        if (ch[i] != '-')
        {
            ans += num * (ch[i] - '0');
            num++;
        }
    }
    cin >> ch[13];
    if (ch[13] - '0' == ans % 11)
        cout << "Right";
    else
    {
        for (int i = 1; i <= 12; i++)
        {
            cout << ch[i];
        }
        cout << ans % 11;
    }
    return 0;
}