import bisect
import copy
import decimal
import fractions
import heapq
import itertools
import math
import random
import sys
import time
from collections import Counter,deque,defaultdict
from functools import lru_cache,reduce
from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max
def _heappush_max(heap,item):
    heap.append(item)
    heapq._siftdown_max(heap, 0, len(heap)-1)
def _heappushpop_max(heap, item):
    if heap and item < heap[0]:
        item, heap[0] = heap[0], item
        heapq._siftup_max(heap, 0)
    return item
from math import gcd as GCD
read=sys.stdin.read
readline=sys.stdin.readline
readlines=sys.stdin.readlines
write=sys.stdout.write

def Extended_Euclid(n,m):
    stack=[]
    while m:
        stack.append((n,m))
        n,m=m,n%m
    if n>=0:
        x,y=1,0
    else:
        x,y=-1,0
    for i in range(len(stack)-1,-1,-1):
        n,m=stack[i]
        x,y=y,x-(n//m)*y
    return x,y

def LCM(n,m):
    if n or m:
        return abs(n)*abs(m)//math.gcd(n,m)
    return 0

def CRT(remainder_lst,mod_lst):
    assert len(remainder_lst)==len(mod_lst)
    if not remainder_lst:
        return 0,1
    remainder,mod=remainder_lst[0],mod_lst[0]
    for r,m in zip(remainder_lst[1:],mod_lst[1:]):
        if (r,m)==(-1,0):
            remainder,mod=-1,0
            break
        r%=m
        g=math.gcd(mod,m)
        lcm=LCM(mod,m)
        if remainder%g!=r%g:
            remainder,mod=-1,0
            break
        remainder,mod=(r+m*((remainder-r)//g)*Extended_Euclid(m//g,mod//g)[0])%lcm,lcm
    return remainder,mod

R,M=[],[]
for _ in range(2):
    m,r=map(int,readline().split())
    R.append(r)
    M.append(m)
r,m=CRT(R,M)
if r==-1:
    ans="NaN"
else:
    ans=r
print(ans)