na982

#include <stdio.h>
#include <algorithm>
#include <queue>
using namespace std;

struct POSI {
	int y, x;
};

int n, l, r;
int map[50][50];

void create_area(int sy, int sx, int status[][50], int index, int& count, int& sum) {
	int visited[50][50] = { 0, };

	const int dy[] = { 0, 0, -1, +1 };
	const int dx[] = { -1, +1, 0, 0 };

	queue<posi> q;
	POSI head;
	head.y = sy;
	head.x = sx;
	visited[sy][sx] = 1;
	q.push(head);

	while (!q.empty()) {
		POSI cur = q.front();	q.pop();

		status[cur.y][cur.x] = index;
		++count;
		sum += map[cur.y][cur.x];

		for (int dir = 0; dir < 4; ++dir) {
			POSI next;
			next.y = cur.y + dy[dir];
			next.x = cur.x + dx[dir];

			if (next.y < 0 || next.y >= n || next.x < 0 || next.x >= n) {
				continue;
			}

			int delta = abs(map[cur.y][cur.x] - map[next.y][next.x]);
			if (visited[next.y][next.x] == 0 && l <= delta && delta <= r) {
				visited[next.y][next.x] = 1;
				q.push(next);
			}
		}
	}
}


int main()
{
	scanf("%d %d %d", &n, &l, &r);
	for (int y = 0; y < n; ++y) {
		for (int x = 0; x < n; ++x) {
			scanf("%d", &map[y][x]);
		}
	}

	int ret = 0;
	bool is_update = true;
	while (is_update) {
		is_update = false;

		int status[50][50] = { 0, };
		int area_index = 0;
		int count[2501] = { 0, };
		int sum[2501] = { 0, };
		for (int y = 0; y < n; ++y) {
			for (int x = 0; x < n; ++x) {
				if (status[y][x] == 0) {
					++area_index;
					create_area(y, x, status, area_index, count[area_index], sum[area_index]);
				}
			}
		}

		for (int y = 0; y < n; ++y) {
			for (int x = 0; x < n; ++x) {
				int  index = status[y][x];
				int avg = sum[index] / count[index];
				if (map[y][x] != avg) {
					map[y][x] = avg;
					is_update = true;					
				}
			}
		}
		if (is_update) {
			++ret;
		}
	}

	printf("%d\n", ret);
	return 0;
}