source_code: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.Reader;
  import java.util.*;
  public class F {
      public static void main(String[] args) {
          FastScanner scanner = new FastScanner();
          int N = scanner.nextInt();
          int M = scanner.nextInt();
          int[][] matrix = new int[N][M];
          for(int i = 0; i < N; i++) {
              for(int j = 0; j < M; j++) {
                  matrix[i][j] = scanner.nextInt();
              }
          }
          int[][] maxDist = new int[N][N];
          for(int i = 0; i < N; i++) {
              Arrays.fill(maxDist[i], Integer.MAX_VALUE);
          }
          for(int i = 0; i < M; i++) {
              for(int  j = 0; j < N; j++) {
                  for(int k = j+1; k < N; k++) {
                      maxDist[j][k] = Math.min(maxDist[j][k], Math.abs(matrix[k][i] - matrix[j][i]));
                      maxDist[k][j] = maxDist[j][k];
                  }
              }
          }
          int[][] distTop = new int[N][N];
          for(int i = 0; i < N; i++) {
              Arrays.fill(distTop[i], Integer.MAX_VALUE);
          }
          for(int i = 0; i < M-1; i++) {
              for(int j = 0; j < N; j++) {
                  for(int k = 0; k < N; k++) {
                      distTop[j][k] = Math.min(distTop[j][k], Math.abs(matrix[j][i] - matrix[k][i+1]));
                  }
              }
          }
          if (N == 1) {
              System.out.println(distTop[0][0]);
              System.exit(0);
          }
          int[] bitLoc = new int[1<<N];
          for(int i = 0; i < N; i++) {
              bitLoc[1 << i] = i;
          }
          int[][][] dp = new int[1<<N][N][N];
          //iterate over every row
          for(int mask = 1; mask < (1 << N); mask++) {
              for(int smask = mask; smask > 0; smask &= (smask-1)) {
                  int i = bitLoc[Integer.lowestOneBit(smask)];
                  for (int ss = mask ^ 1 << i; ss > 0; ss &= ss - 1) {
                      int j = bitLoc[Integer.lowestOneBit(ss)];
                      if (mask == (1 << i ^ 1 << j))
                          dp[mask][i][j] = maxDist[i][j];
                      else {
                          int x = 0;
                          for (int sss = mask ^ 1 << i ^ 1 << j; sss > 0; sss &= sss - 1) {
                              int k = bitLoc[sss & -sss];
                              x = Math.max(x, Math.min(dp[mask ^ 1 << j][i][k], maxDist[k][j]));
                          }
                          dp[mask][i][j] = x;
                      }
                  }
              }
          }
          int mxMsk = (1 << N) -1;
          int max = 0;
          for(int i = 0; i < N; i++) {
              for(int j = 0; j < N; j++) {
                  if (i==j) continue;
                  max = Math.max(max, Math.min(dp[mxMsk][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;
          }
      }
  }
  