source_code: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.Reader;
  import java.util.Arrays;
  import java.util.StringTokenizer;
  
  public class ElongatedMatrix2 {
      public static void main(String[] args) {
          FastScanner scanner = new FastScanner();
          int N = scanner.nextInt();
          int M = scanner.nextInt();
          int[][] arr = new int[N][M];
          for(int i = 0; i < N; i++) {
              for(int j = 0; j < M; j++) {
                  arr[i][j] = scanner.nextInt();
              }
          }
          int[][] distRow = new int[N][N];
          int[][] distTop = new int[N][N];
  //        for(int i = 0; i < N; i++) {
  //            Arrays.fill(distTop, Integer.MAX_VALUE);
  //            Arrays.fill(distRow, Integer.MAX_VALUE);
  //        }
          //compute row distances
          for(int i = 0; i < N; i++) {
              for(int j = i+1; j < N; j++) {
                  int curMin = Integer.MAX_VALUE;
                  for(int k = 0; k < M; k++) {
                      curMin = Math.min(curMin, Math.abs(arr[i][k] - arr[j][k]));
                  }
                  distRow[i][j] = distRow[j][i] = curMin;
              }
          }
          //compute bottom/top distances
          for(int i = 0; i < N; i++) {
              for(int j = 0; j < N; j++) {
                  int curMin = Integer.MAX_VALUE;
                  for(int k = 0; k+1 < M; k++) {
                      curMin = Math.min(curMin, Math.abs(arr[i][k] - arr[j][k+1]));
                  }
                  distTop[i][j] = curMin;
              }
          }
          int maxMask = 1 << N;
          int[][][] dp = new int[maxMask][N][N];
          for(int i = 0; i < maxMask; i++) {
              for(int j = 0; j < N; j++) {
                  Arrays.fill(dp[i][j], Integer.MAX_VALUE);
              }
          }
          for(int mask = 1; mask < maxMask; mask++) {
              for (int j = 0; j < N; j++) {
                  if ((mask & ( 1 << j)) == 0) continue;
                  for(int k = 0; k < N; k++) {
                      if ((mask &(1 << k)) == 0) continue;
                      if (j == k && mask - (1 << k) != 0) continue;
                      for (int i = 0; i < N; i++) {
                          if ((mask & (1 << i)) > 0) continue;
                          int curMask = mask | (1 << i);
                          if (dp[curMask][i][k] != Integer.MAX_VALUE)
                              dp[curMask][i][k] = Math.max(dp[curMask][i][k], Math.min(dp[mask][j][k], distRow[i][j]));
                          else
                              dp[curMask][i][k] = Math.min(dp[mask][j][k], distRow[i][j]);
                      }
                  }
              }
          }
          maxMask--;
          int max = 0;
          for(int i= 0; i < N; i++) {
              for(int j = 0; j < N; j++) {
                  if (i==j && N != 1) continue;
                  max = Math.max(max, Math.min(dp[maxMask][i][j], distTop[i][j]));
              }
          }
          System.out.println(max);
      }
      public static class FastScanner {
          BufferedReader br;
          StringTokenizer st;
          public FastScanner(Reader in) {
              br = new BufferedReader(in);
          }
          public FastScanner() {
              this(new InputStreamReader(System.in));
          }
          String next() {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
          int nextInt() {
              return Integer.parseInt(next());
          }
          long nextLong() {
              return Long.parseLong(next());
          }
          double nextDouble() {
              return Double.parseDouble(next());
          }
          String readNextLine() {
              String str = "";
              try {
                  str = br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
              }
              return str;
          }
          int[] readIntArray(int n) {
              int[] a = new int[n];
              for (int idx = 0; idx < n; idx++) {
                  a[idx] = nextInt();
              }
              return a;
          }
      }
  }
  