#include <bits/stdc++.h>
#define FASTIO
using namespace std;

using ll = long long;
using Vi = std::vector<int>;
using Vl = std::vector<ll>;
using Pii = std::pair<int, int>;
using Pll = std::pair<ll, ll>;

constexpr int I_INF = std::numeric_limits<int>::max();
constexpr ll L_INF = std::numeric_limits<ll>::max();

template <typename T1, typename T2>
inline bool chmin(T1& a, const T2& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <typename T1, typename T2>
inline bool chmax(T1& a, const T2& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <std::ostream& os = std::cout>
class Prints {
private:
    class __Prints {
    public:
        __Prints(const char* sep, const char* term) : sep(sep), term(term) {}
        template <class... Args>
#if __cplusplus >= 201703L
        auto operator()(const Args&... args) const -> decltype((os << ... << std::declval<Args>()), void()) {
#else
        void operator()(const Args&... args) const {
#endif
            print(args...);
        }
        template <typename T>
#if __cplusplus >= 201703L
        auto pvec(const T& vec, size_t sz) const -> decltype(os << std::declval<decltype(std::declval<T>()[0])>(), void()) {
#else
        void pvec(const T& vec, size_t sz) const {
#endif
            for (size_t i = 0; i < sz; i++)
                os << vec[i] << (i == sz - 1 ? term : sep);
        }
        template <typename T>
#if __cplusplus >= 201703L
        auto pmat(const T& mat, size_t h, size_t w) const -> decltype(os << std::declval<decltype(std::declval<T>()[0][0])>(), void()) {
#else
        void pmat(const T& mat, size_t h, size_t w) const {
#endif
            for (size_t i = 0; i < h; i++)
                for (size_t j = 0; j < w; j++)
                    os << mat[i][j] << (j == w - 1 ? term : sep);
        }

    private:
        const char *sep, *term;
        void print() const { os << term; }
        void print_rest() const { os << term; }
        template <class T, class... Tail>
        void print(const T& head, const Tail&... tail) const { os << head, print_rest(tail...); }
        template <class T, class... Tail>
        void print_rest(const T& head, const Tail&... tail) const { os << sep << head, print_rest(tail...); }
    };

public:
    Prints() {}
    __Prints operator()(const char* sep = " ", const char* term = "\n") const { return __Prints(sep, term); }
};

Prints<> prints;
Prints<std::cerr> prints_err;

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

template <typename T>
constexpr std::pair<T, T> extended_euclidean(const T& a, const T& b) {
    T x = 1, y = 0, u = 0, v = 1, s = a, t = b;
    T k = 0, tmp = 0;
    while (t) {
        k = s / t, s -= k * t;
        tmp = s, s = t, t = tmp;
        x -= k * u;
        tmp = x, x = u, u = tmp;
        y -= k * v;
        tmp = y, y = v, v = tmp;
    }
    return {x, y};
}

void solve() {
    ll N, M;
    cin >> N >> M;
    Vl A(N), B(M);
    for (ll i = 0; i < N; i++) {
        cin >> A[i];
    }
    for (ll i = 0; i < M; i++) {
        cin >> B[i];
    }

    auto [p, q] = extended_euclidean(N, M);
    ll d = N * p + M * q;
    ll l = N * M / d;

    ll ans = L_INF;
    for (ll i = 0; i < N; i++) {
        for (ll j = 0; j < M; j++) {
            if (A[i] == B[j] && (j - i) % d == 0) {
                ll s = (j - i) / d;
                ll x = i + s * N * p;
                x %= l;
                if (x < 0) x += l;
                chmin(ans, x);
            }
        }
    }

    if (ans == L_INF) {
        prints()(-1);
    } else {
        prints()(ans + 1);
    }
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

int main() {
#ifdef FASTIO
    std::cin.tie(nullptr), std::cout.tie(nullptr);
    std::ios::sync_with_stdio(false);
#endif
#ifdef FILEINPUT
    std::ifstream ifs("./in_out/input.txt");
    std::cin.rdbuf(ifs.rdbuf());
#endif
#ifdef FILEOUTPUT
    std::ofstream ofs("./in_out/output.txt");
    std::cout.rdbuf(ofs.rdbuf());
#endif
    std::cout << std::setprecision(18) << std::fixed;
    solve();
    std::cout << std::flush;
    return 0;
}