import java.util.*;

public class MaximumZeroSubmatrix {

	public static int maximumZeroSubmatrix(int[][] a) {
		int R = a.length;
		int C = a[0].length;

		int res = 0;
		int[] d = new int[C];
		Arrays.fill(d, -1);
		int[] d1 = new int[C];
		int[] d2 = new int[C];
		int[] st = new int[C];
		for (int r = 0; r < R; ++r) {
			for (int c = 0; c < C; ++c)
				if (a[r][c] == 1)
					d[c] = r;
			int size = 0;
			for (int c = 0; c < C; ++c) {
				while (size > 0 && d[st[size - 1]] <= d[c]) --size;
				d1[c] = size == 0 ? -1 : st[size - 1];
				st[size++] = c;
			}
			size = 0;
			for (int c = C - 1; c >= 0; --c) {
				while (size > 0 && d[st[size - 1]] <= d[c]) --size;
				d2[c] = size == 0 ? C : st[size - 1];
				st[size++] = c;
			}
			for (int j = 0; j < C; ++j)
				res = Math.max(res, (r - d[j]) * (d2[j] - d1[j] - 1));
		}
		return res;
	}

	// random test
	public static void main(String[] args) {
		Random rnd = new Random(1);
		for (int step = 0; step < 1000; step++) {
			int R = rnd.nextInt(10) + 1;
			int C = rnd.nextInt(10) + 1;
			int[][] a = new int[R][C];
			for (int r = 0; r < R; r++)
				for (int c = 0; c < C; c++)
					a[r][c] = rnd.nextInt(2);
			int res1 = maximumZeroSubmatrix(a);
			int res2 = slowMaximumZeroSubmatrix(a);
			if (res1 != res2)
				throw new RuntimeException(res1 + " " + res2);
		}
	}

	static int slowMaximumZeroSubmatrix(int[][] a) {
		int res = 0;
		int R = a.length;
		int C = a[0].length;
		for (int r2 = 0; r2 < R; r2++)
			for (int c2 = 0; c2 < C; c2++)
				for (int r1 = 0; r1 <= r2; r1++)
					m1:for (int c1 = 0; c1 <= c2; c1++) {
						for (int r = r1; r <= r2; r++)
							for (int c = c1; c <= c2; c++)
								if (a[r][c] != 0)
									continue m1;
						res = Math.max(res, (r2 - r1 + 1) * (c2 - c1 + 1));
					}
		return res;
	}
}