import sys def input(): return sys.stdin.readline().strip() def list2d(a, b, c): return [[c] * b for i in range(a)] def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)] def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)] def ceil(x, y=1): return int(-(-x // y)) def INT(): return int(input()) def MAP(): return map(int, input().split()) def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)] def Yes(): print('Yes') def No(): print('No') def YES(): print('YES') def NO(): print('NO') sys.setrecursionlimit(10 ** 9) INF = 10 ** 18 MOD = 10 ** 9 + 7 EPS = 10 ** -10 def bfs(src): """ BFS(一般グラフ、重みなし) """ from collections import deque que = deque([src]) dist = {} dist[src] = 0 while que: ux, uy = que.popleft() if abs(ux) > MAX and abs(uy) > MAX: continue if ux == uy: return dist[(ux, uy)] vx, vy = uy, ux if (vx, vy) not in dist: dist[(vx, vy)] = dist[(ux, uy)] + 1 que.append((vx, vy)) vx, vy = ux + uy, ux - uy if (vx, vy) not in dist: dist[(vx, vy)] = dist[(ux, uy)] + 1 que.append((vx, vy)) return -1 x, y = MAP() if x % 2 != y % 2: print(-1) exit() MAX = 100 res = bfs((x, y)) print(res)