import std.algorithm, std.container, std.conv, std.math, std.range, std.typecons, std.stdio, std.string;

auto rdsp(){return readln.splitter;}
void pick(R,T)(ref R r,ref T t){t=r.front.to!T;r.popFront;}
void readV(T...)(ref T t){auto r=rdsp;foreach(ref v;t)pick(r,v);}

void main()
{
  int x, y; readV(x, y);

  if (x != 0 && y != 0 && x.abs != y.abs) {
    writeln(-1);
    return;
  }

  auto a = [[5, 6, 7], [4, 1, 1], [3, 2, 1]];
  auto d = [1, 0, 2, 3, 1, 0, 2, 3];
  writeln(d[a[y.sgn+1][x.sgn+1]]);
}

auto sgn(T)(T n) { return n > 0 ? 1 : n < 0 ? -1 : 0; }