70分求助

#include <iostream>
#include <cstring>
using namespace std;
int main() {
	char a[14];
	cin >> a;
	int i, j = 0, sum = 0, mod;
	for (int i = 0; i <= 11; i++) {
		if (a[i] >= '0' && a[i] <= '9') {
			j++;
			sum += (a[i] - '0') * j;
		}
	}
	mod = sum % 11;
	if ((mod == a[12] - '0') || (mod == 10 && a[12] == 'X')) {
		cout << "right" << endl;
	} else {
		if (mod == 10) {
			a[12] = 'X';
			cout << a << endl;
		} else {
			a[12] = mod + '0';
			cout << a << endl;
		}
	}
	return 0;
}