Problems with functions

[Mariusmssj]

well here i have a program with 2 functions 1st one is to send 2 coordinates of the objects and calculate the distance between then, 2nd one is to tell how close they are apart and display a message

i think i have messed up with the types of the functions i used but since i am new at it, i am having hard time understanding where is the problem, could anyone tell me how and why is it there

#include<iostream>
#include <math.h> 

double EUC(double, double);
std::string message(double);

int main()
{
	int x1,y1 = 0; //coordinates of 1st object
	int x2,y2 = 0; //coordinates of 2nd object
	double rx,ry = 0; //final values of coordinates will be stored in these 2 integers
	double distance = 0; // answers will be stored is this integer
	std::string collision;
	
	std::cout<< "Please enter your 1st object coordinates""\n";
	std::cout<< "X: ";
	std::cin>> x1;
	std::cout<< "Y: ";
	std::cin>> y1;

	std::cout<< "Please enter your 2nd object coordinates""\n";
	std::cout<< "X: ";
	std::cin>> x2;
	std::cout<< "Y: ";
	std::cin>> y2;

	rx = x2 - x1; //takes away 1st object coordinates from the 1st one
	ry = y2 - y1; //takes away 1st object coordinates from the 1st one

	distance = EUC(rx, ry);

	std::cout<< "Distance between 1st and 2nd object is: " << distance << "\n"; //displays the output and the value of distance
	collision = message(distance);
	std::cout<< collision;

}
double EUC(double x, double y)
{
	
	double answer;
	//Pythagorean theorem a^2+b^2=c^2/ which is rx^2+ry^2=distance^2
	answer = x * x + y * y;
	answer = sqrt(answer);
	return(answer);
}

std::string message(double close)
{
	std::string rtn_msg;
	if((close>=0)||(close>=3))
	{
		rtn_msg = "A collision has accoured";
	}
	else if ((close>=4)||(close>=6))
	{
		rtn_msg = "Near miss has accoured";
	}
	else
	{
		rtn_msg = "Objects are far apart";
	}
	return(rtn_msg);
}

rerror: 1 euc_main.cpp(34) : error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'std::string' (or there is no acceptable conversion)

thanks in advance guy ^^