//---
                std::vector<std::pair<std::string, std::string>> vec_str;
                vec_str.push_back(std::make_pair("key-1","val-1"));
		vec_str.push_back(std::make_pair("key-2","val-2"));
		vec_str.push_back(std::make_pair("key-3","val-3"));
		int k=0;
		for(std::vector<std::pair<std::string, std::string>>::iterator it=vec_str.begin(); it != vec_str.end(); ++it )
		{
			std::stringstream ss;
			ss << ++k;

			std::cout << ((std::pair<std::string, std::string>)(*it)).first
					<< " = "
					<< ((std::pair<std::string, std::string>)(*it)).second
					<< std::endl;

			((std::pair<std::string, std::string>)(*it)).second = "new-val-"+ss.str(); // update second of pair !!!
		}

		std::cout << "---" << std::endl;
		for(std::vector<std::pair<std::string, std::string>>::iterator it=vec_str.begin(); it != vec_str.end(); ++it )
		{
			std::cout << ((std::pair<std::string, std::string>)(*it)).first
					<< " = "
					<< ((std::pair<std::string, std::string>)(*it)).second
					<< std::endl;
		}
//---