Высшая проба_единственный номер

#include <iostream>
#include <cmath>
#include <vector>
#include <set>
#include <string>
#include <algorithm>
using namespace std;
using ll = long long;
void co(vector <int> v){
    for (auto x: v) cout<<x<<' ';
    cout<<'\n';
}

struct p{
    int x, y, clr;
};

int x_hlp(int x1, int y1, int x2, int y2){
    int xh1, xh2, yh; //help
    yh = y2;
    //cout<<"yh = "<<yh<<'\n';
    int dif = abs(y1 - yh);
    //cout<<"dif = "<<dif<<'\n';
    xh1 = x1 - dif;
    xh2 = x1 + dif;
    return xh1;
}


//color = {0, 1} = { white, black}

int col(int x, int y){//color
    int xh = x_hlp(x, y, 0, 0);
    //cout<<"xh = "<<xh<<'\n';
    if (abs(xh) % 2 == 0) {
        //white
        return 0;
    }else{
        return 1;
    }
}

void cp(p P, string nm){
    cout<<"point = "<<nm<<'\n';
    cout<<"x = "<<P.x<<"  y = "<<P.y<<"  color = "<<P.clr<<'\n';
}

int y_ln(int x2, int y2, int x_md){//y in line with some (x, y)
    int dif = abs(x2 - x_md);
    int y_ln1, y_ln2;
    y_ln1 = y2 - dif;
    y_ln2 = y2 + dif;
    //они равносильны!
    return y_ln1;
}

int main()
{
    int x1,x2, y1,y2;
    cin>>x1>>y1>>x2>>y2;
    p p1 = {x1, y1};
    p1.clr = col(x1, y1);
    p p2 = {x2, y2};
    p2.clr = col(x2, y2);
    //cp(p1, "p1");
    //cp(p2, "p2");
    bool can;
    if (p1.clr == 0 && p2.clr == 1){
        //cout<<"ONE\n";
        can = 1;
        vector <pair<int,int>> go(8);
        go[0] = {x1 - 1, y1  + 2};
        go[1] = {x1 + 1, y1 + 2};
        go[2] = {x1 + 2, y1 + 1};
        go[3] = {x1 + 2, y1 - 1};
        go[4] = {x1 + 1, y1 - 2};
        go[5] = {x1 - 1, y1 - 2};
        go[6] = {x1 - 2, y1 - 1};
        go[7] = {x1 - 2, y1 + 1};
        bool fast = 0;
        int fast_x, fast_y;
        int X,Y;
        //первый вопрос - супер_fast
        //второй вопрос - fast
        for (auto pnt: go){
            X = pnt.first;
            Y = pnt.second;
            //cout<<"X = "<<X<<" Y = "<<Y<<'\n';
            if (abs(X - x2) == abs(Y - y2)){
                fast = 1;
                if (X == x2 && Y == y2){
                    cout<<1<<'\n';
                    cout<<x2<<' '<<y2<<'\n';
                    exit(0);
                }
                fast_x = X;
                fast_y = Y;
            }
        }
        if (fast){
            cout<<2<<'\n';
            cout<<fast_x<<' '<<fast_y<<'\n';
            cout<<x2<<' '<<y2<<'\n';
        }else{
            X = go[0].first;
            Y = go[0].second;
            int xH = x_hlp(X, Y, x2, y2);
            int x_mid = abs( max(xH,x2) - min(xH, x2)) / 2 + min(xH, x2);
            //cout<<"x_mid = "<<x_mid<<'\n';
            int y_mid = y_ln(x2, y2, x_mid);
            //cout<<"y_mid = "<<y_mid<<'\n';
            cout<<3<<'\n';
            cout<<X<<' '<<Y<<'\n';
            cout<<x_mid<<' '<<y_mid<<'\n';
            cout<<x2<< ' '<<y2<<'\n';
        }
    }
    else if (p1.clr == 1 && p2.clr == 1){
            can = 1;
            //cout<<"TWO\n";
        if (abs(x1 - x2) == abs(y1 - y2)){
            cout<<1<<'\n';
            cout<<x2<<' '<<y2<<'\n';
        }
        else{
            int xh;//проекция точки (x1, y1) на ось y = y2
            xh = x_hlp(x1, y1, x2, y2);
            int x_md;//middle = between min(x1,x2) and max(x1,x2)
            x_md = abs( max(xh,x2) - min(xh, x2)) / 2 + min(xh, x2);
            //cout<<"x_md = "<<x_md<<'\n';
            int y_md = y_ln(x2, y2, x_md);
            //cout<<"y_md = "<<y_md<<'\n';
            cout<<2<<'\n';
            cout<<x_md<<' '<<y_md<<'\n';
            cout<<x2<<' '<<y2<<'\n';
        }

    }
    else can = 0;
    //cout<<"can = "<<can<<'\n';
    if (!can){
        cout<<-1;
        exit(0);
    }

}
//4 2 -8 -1