[aoj]0040

#include <iostream>
#include <string>
#include <sstream>
#include <vector>

using namespace std;
 
string encrypt(string str, int alpha, int beta){
  int size = str.size();
  string ret = "";
 
  for(int i=0;i<size;i++){
	if('a' <= str[i] && str[i] <= 'z'){
	  ret += (alpha * (str[i] - 'a') + beta) % 26 + 'a';
	}
  }
 
  //cout << str << " is encrypted to: "<< ret << endl;
  return ret;
}
 
int main(void){
  string thiss("this");
  string that("that");
  int n;
 
  cin >> n;
  cin.ignore(); //CR+LF
  for(int i=0;i<n;i++){
	vector<string> strv;
	string str, tmp;
	getline(cin, str);
	int numwords;
	istringstream iss(str);
	int alpha, beta;
	bool decided = false;
 
	decided = false;
	while(iss >> tmp){
	  strv.push_back(tmp);
	}
	numwords = strv.size();
 
	for(int j=0;j<numwords;j++){
	  /* test */
	  //cout << "checking: " << strv[j] << endl;
	  /* */
	  if(strv[j].size() == 4){
		if(strv[j][0] == strv[j][3]){// strv[j] is a candidate of that
		  //cout << "candidate of that" << endl;
		  beta = strv[j][2] - 'a';
		  //cout << "beta is " << beta << endl;
		  //calc alpha
		  int k=0;
		  while(strv[j][0] - 'a' +k*26 < beta || (k*26 + strv[j][0] - 'a' - beta) % 19 != 0){ // 19 == t
			k++;
		  }
		  alpha = (k*26+(strv[j][0] - 'a' - beta)) / 19;
		  //cout << "alpha is " << alpha << endl;
		  string encrypted = "";
		  encrypted = encrypt("that", alpha, beta);
		  if(strv[j] == encrypted){
			decided = true;
		  }
		}else{// strv[j] is a candidate of this
		  //cout << "candidate of this" << endl;
		  tmp = strv[j];
		  if(tmp[0] < tmp[3]) tmp[0] += 26;
		  alpha = tmp[0] - tmp[3];
		  //cout << "alpha is " << alpha << endl;
		  if(tmp[3] - 'a' >= alpha * 18 % 26){
			beta = tmp[3] - 'a' - alpha * 18 % 26;
		  }else{
			beta = tmp[3] - 'a' + 26 - alpha * 18 % 26;
		  }
		  //cout << "beta is " << beta << endl;
		  string encrypted = encrypt("this", alpha, beta);
		  if(strv[j] == encrypted){
			decided = true;
		  }
		}
	  }
	  if(decided) break;
	}
 
	//decrypt
	for(int j=0;j<str.size();j++){
	  int k=0;
	  if('a' <= str[j] && str[j] <= 'z'){
		while(str[j]-'a' + k*26 < beta || (k*26 + str[j] - 'a' - beta) % alpha != 0) k++;
		str[j] = ((k*26 + str[j] - 'a' - beta) / alpha) + 'a';
	  }
	}
	cout << str << endl;
  }
 
  return 0;
}