"""


# coding: utf-8
# Your code here!
import sys
read = sys.stdin.read
readline = sys.stdin.readline 
readlines = sys.stdin.readlines

l,r,m,k = [int(i) for i in read().split()]

def check(a,b): # [a,b]に m の倍数？
    
    if a//M b//m

"""
# coding: utf-8
# Your code here!
import sys
read = sys.stdin.read
readline = sys.stdin.readline 
readlines = sys.stdin.readlines

#n = int(input())
#ab = [[int(i) for i in readline().split()] for _ in range(n)]
a,b = [int(i) for i in read().split()]

M = 10**100
x = b
for i in range(100000):
    if x == 0:
        print(1+i)
        break
    if abs(x) >= M:
        print(-1)
        break
    x = a*x+b
else:
    print(-1)