import sys #input = sys.stdin.readline #input = sys.stdin.buffer.readline #文字列はダメ #sys.setrecursionlimit(1000000) #import math import bisect #import itertools #import random #from heapq import heapify, heappop, heappush from collections import defaultdict #from collections import deque import copy #DeepCopy: hoge = [_[:] for _ in hogehoge] #from functools import lru_cache #@lru_cache(maxsize=None) #MOD = pow(10,9) + 7 MOD = 998244353 #dx = [1,0,-1,0] #dy = [0,1,0,-1] #dx8 = [1,1,0,-1,-1,-1,0,1] #dy8 = [0,1,1,1,0,-1,-1,-1] def main(): b0,c0 = map(int,input().split()) b1,c1 = map(int,input().split()) for x in range(10000000): if (x-c0)%b0 == 0 and (x-c1)%b1 == 0: exit(print(x)) print('NaN') if __name__ == '__main__': main()