from collections import deque
n = int(input())
grid = [list(map(int, input().split())) for _ in range(n)]
count = 0
# 上下左右四个方向
dirs = [(-1, 0), (1, 0), (0, -1), (0, 1)]

for i in range(n):
    for j in range(n):
        if grid[i][j] == 1:
            count += 1
            q = deque([(i, j)])
            grid[i][j] = 0  # 标记为已访问
            while q:
                x, y = q.popleft()
                for dx, dy in dirs:
                    nx, ny = x + dx, y + dy
                    if 0 <= nx < n and 0 <= ny < n and grid[nx][ny] == 1:
                        grid[nx][ny] = 0
                        q.append((nx, ny))

print(count)