multiple definition of a variable in c++ [duplicate]

I have 2 source files and 2 header file.

1. utils.hpp

   #ifndef UTILS_HPP_INCLUDED
   #define UTILS_HPP_INCLUDED
   
   #include <iostream>
   #include <fstream>
   #include <map>
   
   using namespace std;
   int test;
   void display(void);
   

2. utils.cpp

   #include "utils.hpp"
   
   void display(void)
   {
    test = 1;
    cout << test;
   }
   

3. main.hpp

    #ifndef MAIN_HPP_INCLUDED
    #define MAIN_HPP_INCLUDED
    #include "utils.hpp"
    #include<iostream>
    using namespace std;
    int i =0;
    #endif // MAIN_HPP_INCLUDED
   

4. main.cpp

    #include <iostream>
    #include "main.hpp"
   
    using namespace std;
   
    int main()
    {
      display();
      cout << "Hello world!" << endl;
      return 0;
    }
   

what is wrong here? why do i get multiple declaration of the variable?

error:

    test2/utils.hpp:11: multiple definition of `test'; obj\Debug\main.o:C:/Users/test2/utils.hpp:11: first defined here

edited: I did try with extern, i still get the same error.