#include <iostream>
#include <graphics.h>
using namespace std;

int main()
{
    int x1,y1,x2,y2;
    float m;
    cout << "x1: "; cin >> x1;
    cout << "y1: "; cin >> y1;
    cout << "x2: "; cin >> x2;
    cout << "y2: "; cin >> y2;

    m = (double)(y2-y1)/(x2-x1)*-1;

    initwindow(480,320,"test",300,200,false,true);

    for (int x = x1; x<=x2; x++)
    {
        putpixel(x,(double)(m*x),GREEN);
        delay(50);
     }

    closegraph(ALL_WINDOWS);
    cin.get();
}