source_code: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.util.Arrays;
  import java.io.IOException;
  import java.io.UncheckedIOException;
  import java.io.Closeable;
  import java.io.Writer;
  import java.io.OutputStreamWriter;
  import java.io.InputStream;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   */
  public class Main {
      public static void main(String[] args) throws Exception {
          Thread thread = new Thread(null, new TaskAdapter(), "", 1 << 27);
          thread.start();
          thread.join();
      }
  
      static class TaskAdapter implements Runnable {
          @Override
          public void run() {
              InputStream inputStream = System.in;
              OutputStream outputStream = System.out;
              FastInput in = new FastInput(inputStream);
              FastOutput out = new FastOutput(outputStream);
              FElongatedMatrix solver = new FElongatedMatrix();
              solver.solve(1, in, out);
              out.close();
          }
      }
  
      static class FElongatedMatrix {
          public void solve(int testNumber, FastInput in, FastOutput out) {
              int n = in.readInt();
              int m = in.readInt();
              int[][] mat = new int[n][m];
              for (int i = 0; i < n; i++) {
                  for (int j = 0; j < m; j++) {
                      mat[i][j] = in.readInt();
                  }
              }
  
              int[][] minDist = new int[n][n];
              SequenceUtils.deepFill(minDist, (int) 1e9);
              for (int i = 0; i < n; i++) {
                  for (int j = 0; j < n; j++) {
                      for (int k = 0; k < m; k++) {
                          minDist[i][j] = Math.min(minDist[i][j], Math.abs(mat[i][k] - mat[j][k]));
                      }
                  }
              }
              int[][] minDistBetweenHeadAndTail = new int[n][n];
              SequenceUtils.deepFill(minDistBetweenHeadAndTail, (int) 1e9);
              for (int i = 0; i < n; i++) {
                  for (int j = 0; j < n; j++) {
                      for (int k = 1; k < m; k++) {
                          minDistBetweenHeadAndTail[i][j] = Math.min(minDistBetweenHeadAndTail[i][j], Math.abs(mat[i][k] - mat[j][k - 1]));
                      }
                  }
              }
  
              Log2 log2 = new Log2();
              BitOperator bo = new BitOperator();
              int[][][] dp = new int[1 << n][n][n];
              for (int i = 1; i < (1 << n); i++) {
                  if (i == Integer.lowestOneBit(i)) {
                      dp[i][log2.floorLog(i)][log2.floorLog(i)] = (int) 1e9;
                      continue;
                  }
                  for (int j = 0; j < n; j++) {
                      for (int k = 0; k < n; k++) {
                          if (bo.bitAt(i, j) == 0) {
                              continue;
                          }
                          for (int t = 0; t < n; t++) {
                              dp[i][j][k] = Math.max(dp[i][j][k],
                                      Math.min(dp[bo.setBit(i, j, false)][t][k],
                                              minDist[j][t]));
                          }
                      }
                  }
              }
  
              int ans = 0;
              for (int i = 0; i < n; i++) {
                  for (int j = 0; j < n; j++) {
                      ans = Math.max(ans, Math.min(dp[(1 << n) - 1][i][j], minDistBetweenHeadAndTail[j][i]));
                  }
              }
              out.println(ans);
          }
  
      }
  
      static class SequenceUtils {
          public static void deepFill(Object array, int val) {
              if (!array.getClass().isArray()) {
                  throw new IllegalArgumentException();
              }
              if (array instanceof int[]) {
                  int[] intArray = (int[]) array;
                  Arrays.fill(intArray, val);
              } else {
                  Object[] objArray = (Object[]) array;
                  for (Object obj : objArray) {
                      deepFill(obj, val);
                  }
              }
          }
  
      }
  
      static class Log2 {
          public int floorLog(int x) {
              return 31 - Integer.numberOfLeadingZeros(x);
          }
  
      }
  
      static class FastInput {
          private final InputStream is;
          private byte[] buf = new byte[1 << 13];
          private int bufLen;
          private int bufOffset;
          private int next;
  
          public FastInput(InputStream is) {
              this.is = is;
          }
  
          private int read() {
              while (bufLen == bufOffset) {
                  bufOffset = 0;
                  try {
                      bufLen = is.read(buf);
                  } catch (IOException e) {
                      bufLen = -1;
                  }
                  if (bufLen == -1) {
                      return -1;
                  }
              }
              return buf[bufOffset++];
          }
  
          public void skipBlank() {
              while (next >= 0 && next <= 32) {
                  next = read();
              }
          }
  
          public int readInt() {
              int sign = 1;
  
              skipBlank();
              if (next == '+' || next == '-') {
                  sign = next == '+' ? 1 : -1;
                  next = read();
              }
  
              int val = 0;
              if (sign == 1) {
                  while (next >= '0' && next <= '9') {
                      val = val * 10 + next - '0';
                      next = read();
                  }
              } else {
                  while (next >= '0' && next <= '9') {
                      val = val * 10 - next + '0';
                      next = read();
                  }
              }
  
              return val;
          }
  
      }
  
      static class BitOperator {
          public int bitAt(int x, int i) {
              return (x >> i) & 1;
          }
  
          public int setBit(int x, int i, boolean v) {
              if (v) {
                  x |= 1 << i;
              } else {
                  x &= ~(1 << i);
              }
              return x;
          }
  
      }
  
      static class FastOutput implements AutoCloseable, Closeable {
          private StringBuilder cache = new StringBuilder(10 << 20);
          private final Writer os;
  
          public FastOutput(Writer os) {
              this.os = os;
          }
  
          public FastOutput(OutputStream os) {
              this(new OutputStreamWriter(os));
          }
  
          public FastOutput println(int c) {
              cache.append(c).append('\n');
              return this;
          }
  
          public FastOutput flush() {
              try {
                  os.append(cache);
                  os.flush();
                  cache.setLength(0);
              } catch (IOException e) {
                  throw new UncheckedIOException(e);
              }
              return this;
          }
  
          public void close() {
              flush();
              try {
                  os.close();
              } catch (IOException e) {
                  throw new UncheckedIOException(e);
              }
          }
  
          public String toString() {
              return cache.toString();
          }
  
      }
  }
  
  