#include <iostream>

// Why does this source code not compile?
//
// First, examine the code and try to
// identify the problem without compiling it.
//
// If you cannot find the problem, compile
// the code and use the compiler's error
// message as a hint.
//
// If you still cannot find the problem,
// scroll down.

// Function declaration
int main();

// Function definition
int main() {
    std::cout << "Hello World!"
              << std::endl

    return 0;
}


















































// The statement
//
//     std::cout << "Hello World!" << std::endl
//
// must end with a semicolon:
//
//     std::cout << "Hello World!" << std::endl;
//
// Without the semicolon, the compiler treats
// the next line as a continuation of the same
// statement. It therefore effectively sees
// something like
//
//     std::cout << "Hello World!" << std::endl return 0;
//
// which is not valid C++.