Is this "subItem = citem.substr(12,3);"possible?

I tried using the sub string funtion that i found on string::substr - C++ Reference

But it doesn't seem to work. here's the code below, could anyone tell me if I have done something wrong because i'm quite novice at C++.

Problem line:

Code:

subItem = citem.substr(12,3);

Full code:

Code:

#include <iostream>
#include <vector>
#include <string>

using namespace std;

int main ()
{
    
string subItem;    
string citem = "0123456789ABCDEFGH";     
subItem = citem.substr(12,3);
cout << subItem;

}

Do i have to do something with .c_str()? I thought that i needed it, but it doesn't seem to help, unless i don't know how to use it.

subItem = citem.substr(3,12 );
is possibly what you meant to write.
Can't guess better unless I buy a crystal ball .

edit:nevermind i figured it out