source_code: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintWriter;
  import java.util.Arrays;
  import java.util.Scanner;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   */
  public class Main {
      public static void main(String[] args) {
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          Scanner in = new Scanner(inputStream);
          PrintWriter out = new PrintWriter(outputStream);
          TaskF solver = new TaskF();
          solver.solve(1, in, out);
          out.close();
      }
  
      static class TaskF {
          public void solve(int testNumber, Scanner in, PrintWriter out) {
              int n = in.nextInt();
              int m = in.nextInt();
              int[][] graph = new int[n][m];
              for (int i = 0; i < n; i++) {
                  for (int j = 0; j < m; j++)
                      graph[i][j] = in.nextInt();
              }
              int[][] mn1 = new int[n][n];
              int[][] mn2 = new int[n][n];
              for (int i = 0; i < n; i++)
                  for (int j = 0; j < n; j++) {
                      int min_val = Integer.MAX_VALUE;
                      for (int k = 0; k < m; k++)
                          min_val = Math.min(min_val, Math.abs(graph[i][k] - graph[j][k]));
                      mn1[i][j] = min_val;
                      min_val = Integer.MAX_VALUE;
                      for (int k = 0; k < m - 1; k++) {
                          min_val = Math.min(min_val, Math.abs(graph[i][k] - graph[j][k + 1]));
                      }
                      mn2[i][j] = min_val;
                  }
              int[][] dp = new int[(1 << (n + 2))][n];
              int ans = 0;
              for (int i = 0; i < n; i++) {
                  for (int[] temp : dp)
                      Arrays.fill(temp, -1);
                  for (int j = 0; j < n; j++) {
                      dp[1 << j][j] = (j == i ? Integer.MAX_VALUE : 0);
  //                dp[1 << j][j] = (j == i ? 0: Integer.MAX_VALUE );
                  }
                  for (int j = 0; j < n; j++) {
                      ans = Math.max(ans, Math.min(mn2[j][i], calc((1 << n) - 1, j, dp, mn1, n)));
                  }
              }
              out.println(ans);
          }
  
          public int calc(int mask, int v, int[][] dp, int[][] mn1, int n) {
  //        System.out.println(mask+","+v);
              if (dp[mask][v] != -1)
                  return dp[mask][v];
              dp[mask][v] = 0;
              for (int u = 0; u < n; u++) {
                  if (u != v && (((mask >> u) & 1) == 1))
                      dp[mask][v] = Math.max(dp[mask][v], Math.min(mn1[u][v], calc(mask ^ (1 << v), u, dp, mn1, n)));
              }
              return dp[mask][v];
          }
  
      }
  }
  
  