private Polyline bridge(Polyline line1, int x1, int y1, Polyline line2, int x2, int y2) {
int dy, dx, s;
Polyline r;
dy = y2 + line2.dy - y1;
if (line2.dy == 0) {
dx = line2.dx;
} else {
s = dy * line2.dx;
dx = s / line2.dy;
}
r = new Polyline(dx, dy, line2.link);
line1.link = new Polyline(x2 + line2.dx - dx - x1, 0, r);
return r;
}
