#include <cstdio> #include <cmath> int main(){ double x1,x2,y1,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; }