friend operator function

I want to write it with friend operator function.this program gives two errors.what's the problem?

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Error   1   error C2678: binary '+' : no operator found which takes a left-hand operand of type 'int' (or there is no acceptable conversion)
IntelliSense: no operator "+" matches these operands  

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#include <iostream>
#include <string>
using namespace std;
class rect
{
	int x,s;
public:
	void input();
	int calc();
	friend int operator + (rect ob,int j);
};
void rect::input()
{
	cout<<"Side:";
	cin>>x;
}
int rect::calc()
{
	return s=x*x;
}

int main()
{
	int f,t;
	cout<<"Enter Area:";
	cin>>f;
	rect obj;
	obj.input();
	obj.calc();
	t=f+obj;
	cout<<t;
	cin.get();
	cin.get();
}

int operator + (rect ob,int j)
{
	return ob.s+j;
}
Also I have a question... :)
What is "friend" attribute? And usage?
Does noone know about this?
Try reversing function args lines 10 and 36. You seek int+rect not rect+int (which you could do with a member function).

@JM: The function (operator+) must be a friend of the rect class so it can refer to the private member s on line 38.
If I want to write it with friend How Should I write?
In this program ,I think friend function is true.
I had not read your talking well .It is working now.
Tanx
You're welcome. Glad you got it. Sorry if my answer was unclear.
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