d = input()
H = []
for i in range(3):
    H.append(input())


def upward():
    if H[1] == 0:
        return None
    d0 = H[0] - H[1]
    d2 = H[2] - H[1]
    return max(d0/d, d2/d, -1) + 1


def downward():
    if H[0] * H[2] == 0:
        return None
    return max((H[1] - min(H[0], H[2]))/d, -1) + 1

ans = min(upward(), downward())
if ans is None:
    print(-1)
else:
    print(ans)