Why doesn't this work? (strings)

Found this code inside accelerated c++...as an exercise....
I don't understand why the code does not work.. the bottom code...
It gives the following error

8 c:\docume~1\pier\mydocu~1\sc103\lab4\untitl~1.cpp
invalid operands `const char[6]' and `const char[7]' to binary `operator +'

Pier.

Code:

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#include <iostream>
#include <string>

int main(void) {
    /*const string hello = "Hello";
    const string message = hello + ", world" + "!"; */ //works
    const string exclam = "!";
    const string message = "Hello" + ",world" + exclam;

    return 0;
}

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You are redefining an object....also you cant use operator+ for 2 strings like that....strings are in namepsace std....once you mark something const, you cant redefine it

Code:

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#include <iostream>
#include <string>
using namespace std;

int main(void) {
    const string hello = "Hello";
    const string message = hello + ", world";
    const string exclam = "!";
   
    cout << message <<  exclam;

    return 0;
}

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