import sys,bisect,string,math,time,functools,random from heapq import heappush,heappop,heapify from collections import deque,defaultdict,Counter from itertools import permutations,combinations,groupby def Golf():*a,=map(int,open(0)) def I():return int(input()) def S_():return input() def IS():return input().split() def LS():return [i for i in input().split()] def LI():return [int(i) for i in input().split()] def LI_():return [int(i)-1 for i in input().split()] def NI(n):return [int(input()) for i in range(n)] def NI_(n):return [int(input())-1 for i in range(n)] def StoLI():return [ord(i)-97 for i in input()] def ItoS(n):return chr(n+97) def LtoS(ls):return ''.join([chr(i+97) for i in ls]) def GI(V,E,ls=None,Directed=False,index=1): org_inp=[];g=[[] for i in range(V)] FromStdin=True if ls==None else False for i in range(E): if FromStdin: inp=LI() a,b,c=(inp+[1])[:3] org_inp.append(inp) else: index=0 a,b,c=(ls[i]+[1])[:3] if index==1:a-=1;b-=1 aa=(a,c);bb=(b,c);g[a].append(bb) if not Directed:g[b].append(aa) return g,org_inp def GGI(h,w,search=None,replacement_of_found='.',mp_def={'#':1,'.':0},boundary=1): #h,w,g,sg=GGI(h,w,search=['S','G'],replacement_of_found='.',mp_def={'#':1,'.':0}) # sample usage mp=[boundary]*(w+2);found={} for i in range(h): s=input() for char in search: if char in s: found[char]=((i+1)*(w+2)+s.index(char)+1) mp_def[char]=mp_def[replacement_of_found] mp+=[boundary]+[mp_def[j] for j in s]+[boundary] mp+=[boundary]*(w+2) return h+2,w+2,mp,found def TI(n):return GI(n,n-1) def bit_combination(k,n=2): rt=[] for tb in range(n**k): s=[tb//(n**bt)%n for bt in range(k)];rt+=[s] return rt def show(*inp,end='\n'): if show_flg:print(*inp,end=end) YN=['YES','NO'];Yn=['Yes','No'] mo=10**9+7 inf=float('inf') l_alp=string.ascii_lowercase #sys.setrecursionlimit(10**7) input=lambda: sys.stdin.readline().rstrip() class Comb: def __init__(self,n,mo=10**9+7): self.fac=[0]*(n+1) self.inv=[1]*(n+1) self.fac[0]=1 self.fact(n) for i in range(1,n+1): self.fac[i]=i*self.fac[i-1]%mo self.inv[n]*=i self.inv[n]%=mo self.inv[n]=pow(self.inv[n],mo-2,mo) for i in range(1,n): self.inv[n-i]=self.inv[n-i+1]*(n-i+1)%mo return def fact(self,n): return self.fac[n] def invf(self,n): return self.inv[n] def comb(self,x,y): if y<0 or y>x: return 0 return self.fac[x]*self.inv[x-y]*self.inv[y]%mo show_flg=False show_flg=True ## Segment Tree ## ## Initializer Template ## # Range Sum: sg=SegTree(n) # Range Minimum: sg=SegTree(n,inf,min,inf) class SegTree: def __init__(self,n,init_ls=None,init_val=0,function=lambda a,b:a+b,ide=0): self.n=n self.ide_ele=ide_ele=ide self.num=num=2**(n-1).bit_length() self.seg=seg=[self.ide_ele]*2*self.num self.lazy=lazy=[self.ide_ele]*2*self.num self.segfun=segfun=function #set_val if init_ls==None: for i in range(n): self.seg[i+self.num-1]=init_val else: for i in range(n): self.seg[i+self.num-1]=init_ls[i] #build for i in range(self.num-2,-1,-1): self.seg[i]=self.segfun(self.seg[2*i+1],self.seg[2*i+2]) def update(self,k,x): k += self.num-1 self.seg[k] = x while k: k = (k-1)//2 self.seg[k] = self.segfun(self.seg[k*2+1],self.seg[k*2+2]) def evaluate(k,l,r): #遅延評価処理 if lazy[k]!=0: node[k]+=lazy[k] if(r-l>1): lazy[2*k+1]+=lazy[k]//2 lazy[2*k+2]+=lazy[k]//2 lazy[k]=0 def query(self,p,q): if q<=p: return self.ide_ele p += self.num-1 q += self.num-2 res=self.ide_ele while q-p>1: if p&1 == 0: res = self.segfun(res,self.seg[p]) if q&1 == 1: res = self.segfun(res,self.seg[q]) q -= 1 p = p//2 q = (q-1)//2 if p == q: res = self.segfun(res,self.seg[p]) else: res = self.segfun(self.segfun(res,self.seg[p]),self.seg[q]) return res def find_min_index(self,p,q,m): if q<=p: return self.ide_ele p += self.num-1 q += self.num-2 res=self.ide_ele while q-p>1: if p&1 == 0: res = self.segfun(res,self.seg[p]) if q&1 == 1: res = self.segfun(res,self.seg[q]) q -= 1 p >>= 1 q = (q-1)//2 if p == q: res = self.segfun(res,self.seg[p]) else: res = self.segfun(self.segfun(res,self.seg[p]),self.seg[q]) return res def __str__(self): # 生配列を表示 rt=self.seg[self.num-1:self.num-1+self.n] return str(rt) class Tree: def __init__(self,inp_size=None,init=True): if init: self.stdin(inp_size) return def stdin(self,inp_size=None): if inp_size==None: self.size=int(input()) else: self.size=inp_size self.edges,_=GI(self.size,self.size-1) return def listin(self,ls): self.size=len(ls)+1 self.edges,_=GI(self.size,self.size-1,ls) return def __str__(self): return str(self.edges) def dfs(self,x,func=lambda prv,nx,dist:prv+dist,root_v=0): q=deque() q.append(x) v=[-1]*self.size v[x]=root_v while q: c=q.pop() for nb,d in self.edges[c]: if v[nb]==-1: q.append(nb) v[nb]=func(v[c],nb,d) return v def EulerTour(self,x,func=lambda prv,nx,dist:prv+dist,root_v=0): q=deque() q.append((-1,x)) v=[None]*self.size v[x]=root_v et=[] while q: cb,ce=q.pop() et.append(ce) for nb,d in self.edges[ce]: if v[nb]==None: q.append((nb,ce)) q.append((ce,nb)) v[nb]=func(v[ce],nb,d) vid=[[-1,-1]for i in range(self.size)] for i,j in enumerate(et): if vid[j][0]==-1: vid[j][0]=i else: vid[j][1]=i return v,et,vid def LCA_init(self,depth,et): self.st=SegTree(self.size*2-1,func=min,ide=inf) for i,j in enumerate(et): self.st.update(i,j) self.LCA_init_stat==True return def LCA(self,root,x,y): if self.LCA_init_stat==False: depth,et,vid=self.EulerTour(root) self.LCA_init(depth,et) return self.st.query(x,y+1) n,m=LI() a=[1,1] b=[1,1] for i in range(n-2): a+=[a[-1]+a[-2]] b+=[b[-1]+b[-2]] d=a[-1]-m ans=0 for i in a[::-1]: if i<=d: d-=i ans+=1 if d!=0: ans=-1 print(ans)