#include <stdio.h> int main() { int x1,x2,y1,y2; double de,dm; scanf("%d %d",&x1,&y1); scanf("%d %d",&x2,&y2); de=sqrt((pow((x1-x2),2))+(pow((y1-y2),2))); dm=abs(x1-x2)+abs(y1-y2); printf("%lf",fabs (de-dm)); return 0; }