N,M = map(int,input().split())
FI = [1,1]
for _ in range(N-2):
    FI.append(FI[-1]+FI[-2])
v = FI[N-1] - M
cnt = 0
for fi in FI[:N-2][::-1]:
    if fi<=v:
        v-=fi
        cnt+=1
    if v==0:
        print(cnt)
        exit()
print(-1)