#include #include #include using namespace std; int main() { double x1,y1,x2,y2,m,n,i,j; cin>>x1>>y1; cin>>x2>>y2; m=x1-x2; n=y1-y2; m=pow(abs(m),2); n=pow(abs(n),2); i=m+n; j=sqrt(i); cout<<setiosflags(ios::fixed)<<setprecision(3)<<j<<endl; return 0; }