text: #include <iostream>
  
  #include "testlib.h"
  using namespace std;
  
  int main() {
      registerValidation();
  
      string s = inf.readToken();
      inf.readChar('\n');
      inf.readEof();
      int n = int(s.size());
      ensure(1 <= n && n <= 500'000);
  
      for (char c: s) {
          ensure(islower(c));
      }
      return 0;
  }
  