#include <iostream> #include <algorithm> #include <cmath> // #define PI arccos(-1) using namespace std; double PI = acos(-1); int main() { double x0,x1,y0,y1,z0,z1; cin>>x0>>y0>>z0>>x1>>y1>>z1; double a = (x0-x1)*(x0-x1)+(y0-y1)*(y0-y1)+(z0-z1)*(...