#include using namespace std; int main(int argc, char const *argv[]) { for (double x1, y1, x2, y2; cin >> x1 >> y1 >> x2 >> y2;) { cout << setiosflags(ios::fixed) << setprecision(2) << hypot(x1 - x2, y1 - y2) << endl; } return 0; }