#include<iostream>
#include<cmath>
using namespace std;
double calc_len(double x[],double y[])
{
return sqrt(pow(x[0] - x[1], 2) + pow(y[0] - y[1], 2));
}
int
main()
{
int i;
double x[2], y[2];
for (i = 0; i < 2; i++) {
cout << "x" << i + 1 << "=";
cin >> x[i];
cout << "y" << i + 1 << "=";
cin >> y[i];
}
cout << "line is " << calc_len(x, y) << endl;
return 0;
}