def I():return int(input())
def MAP():return map(int,input().split())
def MAPs():return map(str,input().split())
def LI(): return list(map(int,input().split()))
def TPL(): return tuple(map(int,input().split()))
def S():return input()
from collections import defaultdict,Counter,deque
from copy import deepcopy
from heapq import heapify,heappop,heappush
from bisect import bisect_left,bisect_right
from itertools import accumulate,product,permutations,combinations,combinations_with_replacement
from math import gcd,ceil,floor,factorial,sqrt,pi,sin,cos,tan,radians,exp
import time
import random
inf=float('inf');mod=998244353;Mod=10**9+7
dydx=[(1,0),(0,1),(-1,0),(0,-1)]

def inv_gcd(a,b):
    a=a%b
    if a==0:
        return (b,0)
    s=b;t=a
    m0=0;m1=1
    while(t):
        u=s//t
        s-=t*u
        m0-=m1*u
        s,t=t,s
        m0,m1=m1,m0
    if m0<0:
        m0+=b//s
    return (s,m0)
def inv_mod(x,m):
    assert 1<=m
    z=inv_gcd(x,m)
    assert z[0]==1
    return z[1]
def crt(r,m):#余り、割る数
    assert len(r)==len(m)
    n=len(r)
    r0=0;m0=1
    for i in range(n):
        assert 1<=m[i]
        r1=r[i]%m[i]
        m1=m[i]
        if m0<m1:
            r0,r1=r1,r0
            m0,m1=m1,m0
        if (m0%m1==0):
            if (r0%m1!=r1):
                return (0,0)
            continue
        g,im=inv_gcd(m0,m1)
        u1=m1//g
        if ((r1-r0)%g):
            return (0,0)
        x=(r1-r0)//g % u1*im%u1
        r0+=x*m0
        m0*=u1
        if r0<0:
            r0+=m0
    return (r0,m0)#ありえない数字だった場合m0が0で返ってくる

def floor_sum(n,m,a,b):
    ans=0
    if a>=m:
        ans+=(n-1)*n*(a//m)//2
        a%=m
    if b>=m:
        ans+=n*(b//m)
        b%=m
    y_max=(a*n+b)//m
    x_max=(y_max*m-b)
    if y_max==0:
        return ans
    ans+=(n-(x_max+a-1)//a)*y_max
    ans+=floor_sum(y_max,a,m,(a-x_max%a)%a)
    return ans

b0,c0=MAP()
b1,c1=MAP()
r,m=crt([c0,c1],[b0,b1])
if m==0:
    print('NaN')
else:
    print(r)