class Solution {
public:
vector<long long> kthPalindrome(vector<int>& queries, int intLength) {
const int start = pow(10, (intLength + 1) / 2 - 1);
const int end = pow(10, (intLength + 1) / 2);
const int mul = pow(10, intLength / 2);
vector<long long> ans;
for (const int query : queries)
if (start + query > end)
ans.push_back(-1);
else
ans.push_back(getKthPalindrome(quyer, start, mul, intLength));
return ans;
}
private:
long long getKthPalindrome(int query, int start, int mul, int intLength) {
const long long prefix = start + query - 1;
return prefix * mul + reverse(intLength & 1 ? prefix / 10 : prefix);
}
long long reverse(int num) {
long long res = 0;
while (num) {
res = res * 10 + num % 10;
num /= 10;
}
return res;
}
};