include[HTML_REMOVED]

include[HTML_REMOVED]

include[HTML_REMOVED]

using namespace std;
int main()
{double x1,y1,x2,y2,M;
cin>>x1>>y1>>x2>>y2;
M=(x1-x2)(x1-x2)+(y1-y2)(y1-y2);
double distance=sqrt(M);
printf(“%.4lf”,distance);
return 0;

}