201312-2 ISBN号码

#include <iostream>
#include <string>
using namespace std;
int main()
{
    string a;
    cin >> a;
    int sum = 0;
    for (int i = 0, j = 1; i + 1 < a.size(); i ++ ) 
        if (a[i] != '-')
        {
            sum += (a[i] - '0') * j;
            j ++;
        }
    sum %= 11;
    char c = sum + '0';
    if (sum == 10) c = 'X';
    if (c == a.back())
        puts("Right");
    else
    {
        a.back() = c;
        cout << a;
    }
    return 0;
}