#line 1 "test.cpp"
//#pragma GCC target("avx")
//#pragma GCC optimize("O3")
//#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#ifdef LOCAL
#include <debug.hpp>
#define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#define debug(...) (static_cast<void>(0))
#endif
using namespace std;
using ll = long long;
using ld = long double;
using pll = pair<ll,ll>;
using pii = pair<int,int>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vpii = vector<pii>;
using vpll = vector<pll>;
using vs = vector<string>;
template<class T> using pq = priority_queue<T,vector<T>,greater<T>>;
#define overload4(_1, _2, _3, _4, name, ...) name
#define overload3(a,b,c,name,...) name
#define rep1(n) for (ll UNUSED_NUMBER = 0; UNUSED_NUMBER < (n); ++UNUSED_NUMBER)
#define rep2(i, n) for (ll i = 0; i < (n); ++i)
#define rep3(i, a, b) for (ll i = (a); i < (b); ++i)
#define rep4(i, a, b, c) for (ll i = (a); i < (b); i += (c))
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep1(n) for(ll i = (n) - 1;i >= 0;i--)
#define rrep2(i,n) for(ll i = (n) - 1;i >= 0;i--)
#define rrep3(i,a,b) for(ll i = (b) - 1;i >= (a);i--)
#define rrep4(i,a,b,c) for(ll i = (a) + ((b)-(a)-1) / (c) * (c);i >= (a);i -= c)
#define rrep(...) overload4(__VA_ARGS__, rrep4, rrep3, rrep2, rrep1)(__VA_ARGS__)
#define all1(i) begin(i),end(i)
#define all2(i,a) begin(i),begin(i)+a
#define all3(i,a,b) begin(i)+a,begin(i)+b
#define all(...) overload3(__VA_ARGS__, all3, all2, all1)(__VA_ARGS__)
#define sum(...) accumulate(all(__VA_ARGS__),0LL)
template<class T> bool chmin(T &a, const T &b){ if(a > b){ a = b; return 1; } else return 0; }
template<class T> bool chmax(T &a, const T &b){ if(a < b){ a = b; return 1; } else return 0; }
template<class T> auto min(const T& a){ return *min_element(all(a)); }
template<class T> auto max(const T& a){ return *max_element(all(a)); }
template<class... Ts> void in(Ts&... t);
#define INT(...) int __VA_ARGS__; in(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__; in(__VA_ARGS__)
#define STR(...) string __VA_ARGS__; in(__VA_ARGS__)
#define CHR(...) char __VA_ARGS__; in(__VA_ARGS__)
#define DBL(...) double __VA_ARGS__; in(__VA_ARGS__)
#define LD(...) ld __VA_ARGS__; in(__VA_ARGS__)
#define VEC(type, name, size) vector<type> name(size); in(name)
#define VV(type, name, h, w) vector<vector<type>> name(h, vector<type>(w)); in(name)
ll intpow(ll a, ll b){ ll ans = 1; while(b){if(b & 1) ans *= a; a *= a; b /= 2;} return ans;}
ll modpow(ll a, ll b, ll p){ ll ans = 1; a %= p;while(b){ if(b & 1) (ans *= a) %= p; (a *= a) %= p; b /= 2; } return ans; }
ll GCD(ll a,ll b) { if(a == 0 || b == 0) return a + b; if(a % b == 0) return b; else return GCD(b,a%b);}
ll LCM(ll a,ll b) { if(a == 0) return b; if(b == 0) return a;return a / GCD(a,b) * b;}
namespace IO{
#define VOID(a) decltype(void(a))
struct setting{ setting(){cin.tie(nullptr); ios::sync_with_stdio(false);fixed(cout); cout.precision(12);}} setting;
template<int I> struct P : P<I-1>{};
template<> struct P<0>{};
template<class T> void i(T& t){ i(t, P<3>{}); }
void i(vector<bool>::reference t, P<3>){ int a; i(a); t = a; }
template<class T> auto i(T& t, P<2>) -> VOID(cin >> t){ cin >> t; }
template<class T> auto i(T& t, P<1>) -> VOID(begin(t)){ for(auto&& x : t) i(x); }
template<class T, size_t... idx> void ituple(T& t, index_sequence<idx...>){
    in(get<idx>(t)...);}
template<class T> auto i(T& t, P<0>) -> VOID(tuple_size<T>{}){
    ituple(t, make_index_sequence<tuple_size<T>::value>{});}
#undef VOID
}
#define unpack(a) (void)initializer_list<int>{(a, 0)...}
template<class... Ts> void in(Ts&... t){ unpack(IO :: i(t)); }
#undef unpack
constexpr int mod = 1000000007;
//constexpr int mod = 998244353;
static const double PI = 3.1415926535897932;
template <class F> struct REC {
    F f;
    REC(F &&f_) : f(forward<F>(f_)) {}
    template <class... Args> auto operator()(Args &&...args) const { return f(*this, forward<Args>(args)...); }};

#line 3 "library/math/garner.hpp"
using namespace std;
#line 3 "library/math/factorize.hpp"
using namespace std;
vector<pair<long long,int>> prime_factorization(long long n) {
    vector<pair<long long,int>> ret;
    int c = 0;
    while(n % 2 == 0) {
        c++;
        n >>= 1;
    }
    if(c) ret.emplace_back(2,c);
    for(long long i = 3; i * i <= n; i += 2) {
        c = 0;
        while(n % i == 0) {
            n /= i;
            c++;
        }
        if(c) ret.emplace_back(i,c);
    }
    if (n != 1) ret.emplace_back(n,1);
    return ret;
}
vector<long long> divisor(long long n) {
    vector<long long> ret;
    for(long long i = 1; i * i <= n; i++) {
        if (n % i == 0) {
            ret.push_back(i);
            if(i * i != n) {ret.push_back(n / i);}
        }
    }
    sort(ret.begin(),ret.end());
    return ret;
}
#line 3 "library/modint/barrett-reduction.hpp"
using namespace std;
struct Barrett {
    using u32 = unsigned int;
    using i64 = long long;
    using u64 = unsigned long long;
    u32 m;
    u64 im;
    Barrett() : m(), im() {}
    Barrett(int n) : m(n), im(u64(-1) / m + 1) {}
    constexpr inline i64 quo(u64 n) {
        u64 x = u64((__uint128_t(n) * im) >> 64);
        u32 r = n - x * m;
        return m <= r ? x - 1 : x;
    }
    constexpr inline i64 rem(u64 n) {
        u64 x = u64((__uint128_t(n) * im) >> 64);
        u32 r = n - x * m;
        return m <= r ? r + m : r;
    }
    constexpr inline pair<i64, int> quorem(u64 n) {
        u64 x = u64((__uint128_t(n) * im) >> 64);
        u32 r = n - x * m;
        if (m <= r) return {x - 1, r + m};
        return {x, r};
    }
    constexpr inline i64 pow(u64 n, i64 p) {
        u32 a = rem(n), r = m == 1 ? 0 : 1;
        while (p) {
            if (p & 1) r = rem(u64(r) * a);
            a = rem(u64(a) * a);
            p >>= 1;
        }
        return r;
    }
};
#line 4 "library/modint/ArbitaryModint.hpp"
using namespace std;

struct ArbitraryModint {
    int x;
    ArbitraryModint():x(0) {}
    ArbitraryModint(int64_t y) {
        int z = y % get_mod();
        if(z < 0) z += get_mod();
        x = z;
    }
    ArbitraryModint &operator+=(const ArbitraryModint &p) {
        if((x += p.x) >= get_mod()) x -= get_mod();
        return *this;
    }
    ArbitraryModint &operator-=(const ArbitraryModint &p) {
        if((x += get_mod() - p.x) >= get_mod()) x -= get_mod();
        return *this;
    }
    ArbitraryModint &operator*=(const ArbitraryModint &p) {
        x = rem((unsigned long long)x * p.x);
        return *this;
    }
    ArbitraryModint &operator/=(const ArbitraryModint &p) {
        *this *= p.inverse();
        return *this;
    }
    ArbitraryModint operator-() const {return ArbitraryModint(-x);};
    ArbitraryModint operator+(const ArbitraryModint &p) const{
        return ArbitraryModint(*this) += p;
    }
    ArbitraryModint operator-(const ArbitraryModint &p) const{
        return ArbitraryModint(*this) -= p;
    }
    ArbitraryModint operator*(const ArbitraryModint &p) const{
        return ArbitraryModint(*this) *= p;
    }
    ArbitraryModint operator/(const ArbitraryModint &p) const {
        return ArbitraryModint(*this) /= p;
    }
    bool operator==(const ArbitraryModint &p) {return x == p.x;}
    bool operator!=(const ArbitraryModint &p) {return x != p.x;}
    ArbitraryModint inverse() const {
        int a = x,b = get_mod(),u = 1,v = 0,t;
        while(b > 0) {
            t = a / b;
            swap(a -= t * b,b);
            swap(u -= t * v,v);
        }
        return ArbitraryModint(u);
    }
    ArbitraryModint pow(int64_t n) const {
        ArbitraryModint ret(1),mul(x);
        while(n > 0) {
            if(n & 1) ret *= mul;
            mul *= mul;
            n >>= 1;
        }
        return ret;
    }
    friend ostream &operator<<(ostream &os,const ArbitraryModint &p) {
        return os << p.x;
    }
    friend istream &operator>>(istream &is,ArbitraryModint &a) {
        int64_t t;
        is >> t;
        a = ArbitraryModint(t);
        return (is);
    }
    int get() const {return x;}
    inline unsigned int rem(unsigned long long p) {return barrett().rem(p);};
    static inline Barrett &barrett() {
        static Barrett b;
        return b;
    }
    static inline int &get_mod() {
        static int mod = 0;
        return mod;
    }
    static void set_mod(int md) {
        assert(0 < md && md <= (1LL << 30) - 1);
        get_mod() = md;
        barrett() = Barrett(md);
    }
};
#line 6 "library/math/garner.hpp"
using mint = ArbitraryModint;
//存在しない時、-1を返す
template<typename T,typename U>
long long garner(vector<T> rem,vector<U> MOD, long long new_mod = -1, bool coprime = true) {
    assert (rem.size() == MOD.size());
    int n = rem.size();
    using u64 = unsigned long long;
    if(!coprime) {
        unordered_map<long long,vector<pair<long long,long long>>> mp;
        for(int i = 0;i < n;++i) {
            for(auto [p,e]:prime_factorization(MOD[i])) {
                int m = 1;
                for(int j = 0;j < e;++j) m *= p;
                mp[p].emplace_back(rem[i] % m,m);
            }
        }
        vector<T> xx;
        vector<U> mm;
        for(auto &[p,dat]:mp) {
            int M = 1;
            int val = 0;
            for(auto &[x,m]:dat) {
                if(M < m) {
                    M = m;
                    val = x;
                }
            }
            for(auto &[x,m]:dat) {
                if((val - x) % m != 0) return -1;
            }
            xx.emplace_back(val);
            mm.emplace_back(M);
        }
        swap(rem,xx);
        swap(MOD,mm);
        n = (int)rem.size();
    }
    vector<ll> cfs(n);
    for(int i = 0;i < n;++i) {
        mint::set_mod(MOD[i]);
        long long a = rem[i];
        long long prod = 1;
        for(int j = 0;j < i;++j) {
            a = (mint(cfs[j]) * (-prod) + a).x;
            prod = (mint(prod) * MOD[j]).x;
        }
        cfs[i] = (mint(prod).inverse() * a).x;
    }
    long long ret = 0;
    long long prod = 1;
    for(int i = 0;i < n;++i) {
        ret += prod * cfs[i];
        prod *= MOD[i];
        if(new_mod != -1) {
            ret %= new_mod;
            prod %= new_mod;
        }
    }
    return ret;
}
#line 87 "test.cpp"

int main() {
    vi b(2),c(2);
    rep(i,2) cin >> b[i] >> c[i];
    rep(i,2) {
        c[i] %= b[i];
        if(c[i] < 0) c[i] += b[i];
    }
    int x = garner<int,int>(c,b,-1,false);
    if(x == -1) cout << "NaN" << '\n';
    else cout << x << '\n';
}