// Problem: 1102_F. Elongated Matrix
// Time complexity: np
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();
    }

  }
}