#include <bits/stdc++.h>

#define NHL mylove();

#define fi first
#define se second
#define int long long

#define range(i, a, op, n, x) for (int i = a; i op n; i += x)
#define e "\n"

#define tieuacma252 signed main

#define Furina ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define NakanoItsuki "RESCUE"
#define NakanoNino freopen(NakanoItsuki".inp", "r", stdin);freopen(NakanoItsuki".out", "w", stdout);
using namespace std;

const int maxn = 1e5+5;
int n, m;
int a[maxn], b[maxn];

bool check(int x){
    for(int i=0; i<n; i++){
        int it = lower_bound(b, b+m, a[i]-x) - b;
        if(it >= m || b[it] > a[i] + x)
        	return false;
    }
    return true;
}

void solve(){
    cin >> n >> m;
    for(int i=0; i<n; i++){
        cin >> a[i];
    }
    for(int i=0; i<m; i++){
        cin >> b[i];
    }
    sort(b, b+m);
    int l=1, r=2e9, ans = -1;
    while(l <= r) {
        int m = (l+r)/2;
        if(check(m)){
            ans = m;
            r = m-1;
        }
        else 
        	l = m+1;
    }
    cout << ans;
}

tieuacma252() {
    Furina
    solve();
    // NakanoNino
    return 0;
}