#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void rread(T& num) {
  num = 0;
  T f = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') num = num * 10 + ch - '0', ch = getchar();
  num *= f;
}
const int inf = 2e9, mod = 1e9 + 7;
const int maxn = 2e5 + 10;
const long double PI = acos(-1.0);
long long gcd(long long a, long long b) { return (a ? gcd(b % a, a) : b); }
void exgcd(long long a, long long b, long long& d, long long& x, long long& y) {
  if (!b) {
    d = a;
    x = 1;
    y = 0;
  } else {
    exgcd(b, a % b, d, y, x);
    y -= x * (a / b);
  }
}
long long power(long long a, long long n) {
  long long p = 1;
  while (n > 0) {
    if (n % 2) {
      p = p * a;
    }
    n >>= 1;
    a *= a;
  }
  return p;
}
long long power(long long a, long long n, long long mod) {
  long long p = 1;
  while (n > 0) {
    if (n % 2) {
      p = p * a;
      p %= mod;
    }
    n >>= 1;
    a *= a;
    a %= mod;
  }
  return p % mod;
}
int n, m;
int a[maxn], b[maxn];
vector<int> pa[maxn], pb[maxn];
pair<long long, int> pp;
vector<pair<long long, int> > ss;
set<long long> fl, gl;
long long phi(long long x) {
  long long gs = sqrt(x + 0.5);
  long long ans = x;
  for (int i = 2; i <= gs; i++)
    if (x % i == 0) {
      ans = ans / i * (i - 1);
      while (x % i == 0) x /= i;
    }
  if (x != 1) {
    ans = ans / x * (x - 1);
  }
  return ans;
}
int main() {
  while (~scanf("%d%d", &n, &m)) {
    int x, y;
    scanf("%d", &x);
    for (int i = 1; i <= x; i++) scanf("%d", &a[i]);
    scanf("%d", &y);
    for (int i = 1; i <= y; i++) scanf("%d", &b[i]);
    long long d = gcd(n, m);
    if (d > x + y) {
      cout << -1 << endl;
      continue;
    }
    for (int i = 0; i < d; i++) pa[i].clear(), pb[i].clear();
    for (int i = 1; i <= x; i++) {
      pa[a[i] % d].push_back(a[i] / d);
    }
    for (int i = 1; i <= y; i++) pb[b[i] % d].push_back(b[i] / d);
    for (int i = 0; i < d; i++)
      if (pa[i].size() == 0 && pb[i].size() == 0) {
        cout << -1 << endl;
        return 0;
      }
    long long ans = 0;
    long long g = n / d, s = m / d;
    long long px = phi(g), py = phi(s);
    for (int i = 0; i < d; i++) {
      sort(pa[i].begin(), pa[i].end());
      sort(pb[i].begin(), pb[i].end());
      if (pa[i].size() != g && pb[i].size() != s) {
        ss.clear();
        gl.clear();
        fl.clear();
        long long sum = 0;
        for (int j = 0; j < pb[i].size(); j++) {
          fl.insert(pb[i][j]);
          long long cur = pb[i][j];
          cur = power(g % s, py - 1, s) * cur % s;
          pp.first = cur;
          pp.second = pb[i][j];
          ss.push_back(pp);
        }
        for (int j = 0; j < pa[i].size(); j++)
          if (fl.count(pa[i][j] % s) == 0) {
            fl.insert(pa[i][j] % s);
            long long cur = pa[i][j] % s;
            cur = power(g % s, py - 1, s) * cur % s;
            pp.first = cur;
            pp.second = pa[i][j];
            ss.push_back(pp);
          }
        sort(ss.begin(), ss.end());
        ss.push_back(ss[ss.size() - 1]);
        long long maxx = 0, id = 0, cc;
        for (int j = 1; j < ss.size(); j++) {
          cc = ss[j].first - ss[j - 1].first - 1;
          if (cc * g + ss[j - 1].second > maxx)
            maxx = cc * g + ss[j - 1].second;
        }
        cc = ss[0].first + s - ss[ss.size() - 1].first - 1;
        if (cc * g + ss[ss.size() - 1].second > maxx)
          maxx = cc * g + ss[ss.size() - 1].second;
        sum = maxx * d + i;
        ss.clear();
        fl.clear();
        gl.clear();
        for (int j = 0; j < pa[i].size(); j++) {
          fl.insert(pa[i][j]);
          long long cur = pa[i][j];
          cur = power(s % g, px - 1, g) * cur % g;
          pp.first = cur;
          pp.second = pa[i][j];
          ss.push_back(pp);
        }
        for (int j = 0; j < pb[i].size(); j++)
          if (fl.count(pb[i][j] % g) == 0) {
            fl.insert(pb[i][j] % g);
            long long cur = pb[i][j] % g;
            cur = power(s % g, px - 1, g) * cur % g;
            pp.first = cur;
            pp.second = pb[i][j];
            ss.push_back(pp);
          }
        sort(ss.begin(), ss.end());
        ss.push_back(ss[ss.size() - 1]);
        maxx = 0, id = 0;
        for (int j = 1; j < ss.size(); j++) {
          cc = ss[j].first - ss[j - 1].first - 1;
          if (cc * s + ss[j - 1].second > maxx)
            maxx = cc * s + ss[j - 1].second;
        }
        cc = ss[0].first + g - ss[ss.size() - 1].first - 1;
        if (cc * s + ss[ss.size() - 1].second > maxx)
          maxx = cc * s + ss[ss.size() - 1].second;
        sum = max(sum, maxx * d + i);
        ans = max(ans, sum);
      } else if (pa[i].size() == g) {
        long long cur = s - 1;
        for (int j = pb[i].size() - 1; j >= 0; j--)
          if (pb[i][j] != cur)
            break;
          else {
            cur--;
          }
        ans = max(ans, cur * d + i);
      } else if (pb[i].size() == s) {
        long long cur = g - 1;
        for (int j = pa[i].size() - 1; j >= 0; j--)
          if (pa[i][j] != cur)
            break;
          else {
            cur--;
          }
        ans = max(ans, cur * d + i);
      }
    }
    cout << ans << endl;
  }
  return 0;
}
