#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int Mod=998244353;
bool f(int mid, vector<int> &towers, vector<int> &cities){
for (int city : cities) {
auto it = lower_bound(towers.begin(), towers.end(), city);
int best = 1e9; // very large
if (it != towers.end()) best = min(best, abs(city - *it)); // tower >= city
if (it != towers.begin()) best = min(best, abs(city - *(--it))); // tower < city
if (best > mid) return false;
}
return true;
}
void solve() {
int n,m;
cin >> n >> m;
vector<int> cities(n), towers(m);
for(int i=0;i<n;i++) cin >> cities[i];
for(int i=0;i<m;i++) cin >> towers[i];
sort(cities.begin(), cities.end());
sort(towers.begin(), towers.end());
int low = 0, high = 1e9, ans = 0;
while(low <= high){
int mid = (low + high) / 2;
if(f(mid, towers, cities)){
ans = mid;
high = mid-1;
}
else{
low = mid+1;
}
}
cout << ans << '\n';
}
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
/*int t;
cin >> t;
while (t--)*/ solve();
return 0;
}
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