#include <cstdio> #include <cmath> int main() { double x1, y1, x2, y2; scanf("%lf%lf", &x1, &y1); scanf("%lf%lf", &x2, &y2); printf("%.4lf\n", sqrt((x1 - x2) * (x1- x2)+(y1 - y2)*(y1 - y2))); return 0; }