第4和8有问题，， 第4个例子我输出的是Right,答案也是Right,,居然是WA？？？

#include<bits/stdc++.h>
using namespace std;
#define ll long long

int main() {
	string str;
	getline(cin, str);
	int a[10];
	a[1] = str[0];
	a[2] = str[2];
	a[3] = str[3];
	a[4] = str[4];
	a[5] = str[6];
	a[6] = str[7];
	a[7] = str[8];
	a[8] = str[9];
	a[9] = str[10];
	int res = 0;
	for (int i = 1; i <= 9; ++i) {
		res += i * (a[i] - '0');
		res %= 11;
	}
	int n = str.size() - 1;
	if (res == 10) {
		if (str[n] == 'X')cout << "Right" << endl;
		else {
			str[n] = 'X'; cout << str << endl;
		}
	}
	else if(res == str[n]-'0')cout << "Right" << endl;
	else {
		str[n] = res + '0';
		cout << str << endl;
	}
	return 0;
}