b0,c0=list(map(int,input()))
b1,c1=list(map(int,input()))
for i in range(1,b0*b1+1):
    if (i-c0)//b0==0 and (i-c1)//b1==0:
        print (i)
        break
    if i==b0*b1+1:
        print("NaN")