#include <iostream>
#include <cmath>
using namespace std;

class Vektor{
    double vx, vy;
  public:
    Vektor(double ux, double uy){
      vx=ux; vy=uy;              
    }
    double pikkus(){
      return sqrt(vx*vx+vy*vy);
    }
};

int main(void){
  Vektor v1(3, 4);
  cout << v1.pikkus() << endl;
  return 0;    
}