#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001



int main(){
	
	vector<long long> r,m;
	rep(i,2){
		long long b,c;
		cin>>b>>c;
		
		c += b * 10000;
		c %= b;
		m.push_back(b);
		r.push_back(c);
	}
	
	auto ans = crt(r,m);
	if(ans.second==0)cout<<"NaN"<<endl;
	else cout<<ans.first<<endl;
	
	return 0;
}