package main

import . "fmt"

func main() {
	var b,c,e,f int
	Scan(&b,&c,&e,&f)
	for i:=0;i<1e6;i++ {
		if (i+-c+1e4*b)%b!=0 {
			continue
		}
		if (i-f+1e4*e)%e!=0 {
			continue
		}
		Println(i)
		return
	}
	Println("NaN")
}