Hungry Hipos

#!/usr/local/bin/python3.7
# -*- coding: utf-8 -*import

def valid(y,x):
    if y>=0 and x>=0 and y<N and x<horizontal_len:
        return True

def find_blocks(y,x):
    Q.append(y)
    Q.append(x)

    dy = [0,1,0,-1]
    dx = [1,0,-1,0]

    while Q:
        y = Q.pop(0)
        x = Q.pop(0)

        for dir in range(len(dy)):
            next_y = y + dy[dir]
            next_x = x + dx[dir]

            if valid(next_y,next_x) and matrix[next_y][next_x] == 1:
                Q.append(next_y)
                Q.append(next_x)
                matrix[next_y][next_x] = -1


N = int(input())

matrix = []
for rows in range(N):
   row = list(map(int, input().split()))
   matrix.append(row)

horizontal_len = len(matrix[0])

blocks = 0

for start_y in range(N):
    for start_x in range(horizontal_len):

        if matrix[start_y][start_x] == 1:
            matrix[start_y][start_x] = -1
            Q=[]

            find_blocks(start_y, start_x)
            blocks +=1

print(blocks)