大佬们，这个怎么只有50分呢？怎么改呢

#include <iostream>
#include <string.h>
using namespace std;
int main()
{
    char str[20];
    cin >> str;
    int len = strlen(str);
    int sum = 0;
    double remainder = 0;
    sum = (str[0]-'0')* 1 + (str[2] -'0')* 2 + (str[3] -'0')* 3 +( str[4]-'0') * 4 + (str[6]-'0') * 5 + (str[7] -'0')* 6 + (str[8]-'0') * 7 + (str[9] -'0')* 8 + (str[10]-'0') * 9;
    remainder = sum % 11;
    if (remainder == str[12]-'0')
    {
        cout << "Right";
    }
    else
    {
        for(int i=0;i<12;i++)
        {
            cout<<str[i];
        }
        cout<<remainder;
    }
    return 0;
}