#include<cstdio>
#include<cmath>
#include<iostream>
#include<string>
#include<cstring>
#include<set>
#include<stack>
#include<numeric>
#include<algorithm>
#include<atcoder/math>
using namespace std;
using namespace atcoder;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; --i)
#define rep2(i, a, b) for (int i = (int)a; i < (int)(b); ++i)
#define rrep2(i, a, b) for (int i = (int)(b)-1; i >= (int)(a); --i)
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
using ll = long long;
// using mint = modint998244353;
// constexpr int inv_2 = 499122177;
int main(){
    // cin.tie(nullptr);
    // std::ios_base::sync_with_stdio(false);
    vector<ll> B(2), C(2);
    for(int i = 0; i < 2; ++i) scanf("%lld %lld", &B[i], &C[i]);
    auto [x, y] = crt(C, B);
    if(!y) printf("NaN\n");
    else printf("%lld\n", x);
    return 0;
}