#include <iostream>
#include <string>
int main() {
std::string str1 = "Hello";
std::string str2 = "World!";
std::string result = str1 + " " + str2;
std::cout << result << std::endl;
return 0;
}
#include <iostream>
#include <string>
int main() {
std::string str1 = "Hello";
std::string str2 = "World!";
str1.append(" ");
str1.append(str2);
std::cout << str1 << std::endl;
return 0;
}