#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, i, j;
  long long int A[100010], B[100010], D[100010], min;
  cin >> n >> m;
  for (i = 0; i < n; i++) {
    cin >> A[i];
    D[i] = 2000000010;
  }
  for (i = 0; i < m; i++) cin >> B[i];
  for (i = 0, j = 0; i < n && j < m;) {
    if (abs(A[i] - B[j]) > D[i]) {
      i++;
      j--;
      continue;
    }
    D[i] = abs(A[i] - B[j]);
    if (j == m - 1)
      i++;
    else
      j++;
  }
  for (i = 0, min = 0; i < n; i++) {
    if (D[i] > min) min = D[i];
  }
  cout << min << endl;
}
