#include <stdio.h> #include #include <math.h> using namespace std; int main() { double Xa , Xb , Ya ,Yb; cin >> Xa >> Xb ; cin >> Ya >> Yb; double x1 = Xa - Ya; double x2 = Xb - Yb; double x = (x1 * x1)+ (x2 * x2); printf("%.3lf\n",sqrt(x));

}