#include <algorithm>
#include <iostream>
#include <string>

int main()
{
  std::string s = "HALLO, Welt";
	
  auto mid = std::partition_point(begin(s), end(s), [](char c) {return c <= 'Z';});

  std::string gut(begin(s),mid);     // ins Toepfchen
  std::string schlecht(mid, end(s)); // ins Kroepfchen
  
  std::cout << gut << " : " << schlecht << '\n';
}