#include <iostream>
#include <math.h>
using namespace std;
class point
{
double x, y;
public: point(double a, double b) { x = a; y = b; }
friend double Distance(const point& p1, const point& p2);
};
double Distance(const point& p1, const point& p2)
{
return sqrt((p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) * (p1.y - p2.y));
}
int main()
{
point p1(1,1), p2(2,2);
cout << Distance(p1, p2) << endl;
return 0;
}
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