int helper(const vector<vector<bool>>& bitmap, int x_diff, int y_diff) {
	int maxLen = 0;
	for (int i = 0; i < bitmap.size(); i++) {
		int cur = 0;
		for (int j = 0; j < bitmap[i].size(); j++) {
			int nx = i + x_diff, ny = j + y_diff;
			if (nx >= 0 && nx < bitmap.size() && ny >= 0 && ny < bitmap[i].size()) {
				cur++;
				maxLen = max(maxLen, cur);
			}
			else {
				cur = 0;
			}
		}
	}
	return maxLen;
}

int find_longest(const vector<vector<bool>>& bitmap) {
	int result = 0;
	result = max(result, helper(bitmap, -1, 0));
	result = max(result, helper(bitmap, 0, -1));
	result = max(result, helper(bitmap, -1, 0));
	result = max(result, helper(bitmap, -1, 0));
	return result;
}