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