#include <iostream>
#include <cmath>
using namespace std;
class punct {
private:
int x,y;

public :
    friend double dist(punct &p1, punct &p2);
    punct (int a , int b)
    {

        x=a;
        y=b;
    }
};
double dist (punct &p1, punct & p2)
{
    return (sqrt(p1.x-p2.x)*(p1.x-p2.x) +(p1.y-p2.y)*(p1.y-p2.y));
}
int main()
{
    punct p1(3,3);
    punct p2(1,7);
    cout<<"d(p1,p2)=";
    cout<<dist(p1,p2);
    return 0;
}