#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <set>
#include <map>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint = modint998244353;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vmi = vector<mint>;
using vvmi = vector<vmi>;
using vvvmi = vector<vvmi>;
#define all(a) (a).begin(), (a).end()
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)

void solve(){
    
}

int main(){
    set<int> st;
    int n, m; cin >> n >> m;
    map<int, int> mp, m2;
    vi s(n), t(m);
    rep(i, n){
        cin >> s[i];
        st.insert(s[i]);
        mp[s[i]]++;
        m2[s[i]]++;
    }
    rep(i, m){
        cin >> t[i];
    }
    int itr = 0;
    while(itr < m){
        int mx = *prev(st.end());
        if(mx < t[itr])break;
        auto it = st.lower_bound(t[itr]);
        int p = *it;
        mp[p]--;

        if(mp[p] == 0)st.erase(p);
        itr++;
    }
    
    if(itr == 0){
        cout << 0 << endl;
        return 0;
    }
    set<int> s2; rep(i, n)s2.insert(s[i]);
    int ans = 0;
    vi v; rep(i, itr)v.push_back(t[i]); sort(all(v));
    rep(i, itr){
        int p = *s2.lower_bound(v[i]);
        ans = max(ans, p - v[i]);
        m2[p]--;
        if(m2[p] == 0)s2.erase(p);
    }cout << ans << endl;

    return 0;
}