source_code: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.PrintWriter;
  import java.io.FilterInputStream;
  import java.io.BufferedInputStream;
  import java.io.InputStream;
  
  /**
   * @author khokharnikunj8
   */
  
  public class Main {
      public static void main(String[] args) {
          new Thread(null, new Runnable() {
              public void run() {
                  new Main().solve();
              }
          }, "1", 1 << 26).start();
      }
  
      void solve() {
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          ScanReader in = new ScanReader(inputStream);
          PrintWriter out = new PrintWriter(outputStream);
          FElongatedMatrix solver = new FElongatedMatrix();
          solver.solve(1, in, out);
          out.close();
      }
  
      static class FElongatedMatrix {
          int[][] G;
          int[][] G1;
  
          public int findIt(int[] map, int n, int start) {
              int[][] mask = new int[1 << n][n];
              for (int i = 0; i < n; i++) mask[(1 << i)][i] = G[start][map[i]];
              for (int i = 1; i < (1 << n); i++) {
                  for (int j = 0; j < n; j++) {
                      for (int k = 0; k < n; k++) {
                          if (k != j && (i & (1 << k)) == 0 && (i & (1 << j)) != 0) {
                              mask[(i | (1 << k))][k] = Math.max(mask[(i | (1 << k))][k], Math.min(mask[i][j], G[map[j]][map[k]]));
                          }
                      }
                  }
              }
              int ans = 0;
              for (int i = 0; i < n; i++) ans = Math.max(ans, Math.min(mask[(1 << n) - 1][i], G1[start][map[i]]));
              return ans;
          }
  
          public void solve(int testNumber, ScanReader in, PrintWriter out) {
              int n = in.scanInt();
              int m = in.scanInt();
              G = new int[n][n];
              G1 = new int[n][n];
              int[][] ar = new int[n][m];
              for (int i = 0; i < n; i++) {
                  for (int j = 0; j < m; j++) {
                      ar[i][j] = in.scanInt();
                  }
              }
              if (n == 1) {
                  int ans = Integer.MAX_VALUE;
                  for (int i = 0; i < m - 1; i++) ans = Math.min(ans, Math.abs(ar[0][i] - ar[0][i + 1]));
                  out.println(ans);
                  return;
              }
              for (int i = 0; i < n; i++) {
                  for (int j = i + 1; j < n; j++) {
                      int min = Integer.MAX_VALUE;
                      for (int k = 0; k < m; k++) min = Math.min(min, Math.abs(ar[i][k] - ar[j][k]));
                      G[i][j] = G[j][i] = min;
                  }
              }
              for (int i = 0; i < n; i++) {
                  for (int j = 0; j < n; j++) {
                      if (i == j) continue;
                      int min = Integer.MAX_VALUE;
                      for (int k = 1; k < m; k++) min = Math.min(min, Math.abs(ar[i][k] - ar[j][k - 1]));
                      G1[i][j] = min;
  
                  }
              }
              int[] map;
              int ans = 0;
              for (int i = 0; i < n; i++) {
                  map = new int[n - 1];
                  int tl = 0;
                  for (int temp = 0; temp < n; temp++) {
                      if (temp == i) continue;
                      map[tl++] = temp;
                  }
                  ans = Math.max(ans, findIt(map, n - 1, i));
  
              }
              out.println(ans);
  
  
          }
  
      }
  
      static class ScanReader {
          private byte[] buf = new byte[4 * 1024];
          private int index;
          private BufferedInputStream in;
          private int total;
  
          public ScanReader(InputStream inputStream) {
              in = new BufferedInputStream(inputStream);
          }
  
          private int scan() {
              if (index >= total) {
                  index = 0;
                  try {
                      total = in.read(buf);
                  } catch (Exception e) {
                      e.printStackTrace();
                  }
                  if (total <= 0) return -1;
              }
              return buf[index++];
          }
  
          public int scanInt() {
              int integer = 0;
              int n = scan();
              while (isWhiteSpace(n)) n = scan();
              int neg = 1;
              if (n == '-') {
                  neg = -1;
                  n = scan();
              }
              while (!isWhiteSpace(n)) {
                  if (n >= '0' && n <= '9') {
                      integer *= 10;
                      integer += n - '0';
                      n = scan();
                  }
              }
              return neg * integer;
          }
  
          private boolean isWhiteSpace(int n) {
              if (n == ' ' || n == '\n' || n == '\r' || n == '\t' || n == -1) return true;
              else return false;
          }
  
      }
  }
  
  