ABC108B.cpp

    #include <iostream>
    #include <math.h>
    using namespace std;
    int main(int argc, char const *argv[]) {
      double x1,y1,x2,y2;
      cin>>x1>>y1>>x2>>y2;
      double dis,a,x3,y3,x4,y4;
      dis=sqrt(pow(x1-x2,2)+pow(y1-y2,2));
      if(x1!=x2){
        a=(y1-y2)/(x1-x2);
        if(a!=0){
          if(y1<=y2){
            x4=x1-dis*sqrt(pow(a,2)/(pow(a,2)+1));
            y4=(x1-x4)/a+y1;
            x3=x2+(x4-x1);
            y3=y2+(y4-y1);
          }else{
            x4=x1+dis*sqrt(pow(a,2)/(pow(a,2)+1));
            y4=(x1-x4)/a+y1;
            x3=x2+(x4-x1);
            y3=y2+(y4-y1);
          }
        }else{
          x3=x2;
          x4=x1;
          if(x1<x2){
            y3=y2+dis;
            y4=y3;
          }else{
            y3=y2-dis;
            y4=y3;
          }
        }
      }else{
        y3=y2;
        y4=y1;
        if(y1<y2){
          x3=x2-dis;
          x4=x1-dis;
        }else{
          x3=x2+dis;
          x4=x1+dis;
        }
      }
      printf("%.0f %.0f %.0f %.0f\n",x3,y3,x4,y4);
      return 0;
    }