import java.util.Scanner;

public class Statues_John {

	public static final int MAXS = 50;

	public static int[][] grid = new int[MAXS][MAXS];
	public static int[][] grid2 = new int[MAXS][MAXS];
	public static int[] sizes = new int[MAXS*MAXS];
	public static int numSizes = 0;

	public static void main(String[] args) {

		Scanner in = new Scanner(System.in);
		int rows, cols;
		rows = in.nextInt();
		cols = in.nextInt();
		for(int i=0; i<rows; i++) {
			for(int j=0; j <cols; j++) {
				int val = in.nextInt();
				grid[i][j] = val;
				if (val != -1)
					sizes[numSizes++] = val;					
			}
		}
		sort(sizes, numSizes);
		int count = place(grid, rows, cols);
		rotate(grid, grid2, rows, cols);
		int val = place(grid2, cols, rows);
		if (val > count)
			count = val;
		rotate(grid2, grid, cols, rows);
		val = place(grid, rows, cols);
		if (val > count)
			count = val;
		rotate(grid, grid2, rows, cols);
		val = place(grid2, cols, rows);
		if (val > count)
			count = val;
		System.out.println(numSizes-count);
	}

	public static void sort(int [] a, int n)
	{
		for(int i=1; i < n; i++) {
			int tmp = a[i];
			int j=i;
			while (j > 0 && a[j-1] > tmp) {
				a[j] = a[j-1];
				j--;
			}
			a[j] = tmp;
		}
	}

	public static int place(int[][] grid, int rows, int cols)
	{
		int numDiags = rows+cols-1;
		int index = 0;								// index into sorted array
		int count = 0;
		for(int i=0; i<numDiags; i++) {
			int startRow = i < cols ? 0 : i-cols+1;
			int endRow = i < rows ? i : rows-1;
			int startCol = i < cols ? i : cols-1;
			int numVals = endRow-startRow+1;		// determine # of values in diagonal		
			int c = startCol;
			for(int r = startRow; r <=  endRow; r++, c--) {
				if (grid[r][c] == -1)
					numVals--;
			}
			if (numVals == 0)
				continue;
			int low = sizes[index];					// range of values in this diagonal
			int high = sizes[index+numVals-1];
			c = startCol;
			for(int r = startRow; r <=  endRow; r++, c--) {
				int val = grid[r][c];
				if (val >= low && val <= high)
					count++;
			}
			index += numVals;

		}
		return count;
	}

	public static void rotate(int[][] a, int[][] b, int rows, int cols)
	{
		for(int r=0; r<rows; r++) 
			for(int c=0; c<cols; c++)
				b[c][rows-r-1] = a[r][c];
	}

	public static void printGrid(int[][] a, int rows, int cols)
	{
		for(int r=0; r<rows; r++) {
			for(int c=0; c<cols; c++) {
				System.out.print(a[r][c] + " ");
			}
			System.out.println();
		}
	}
}