#include<iostream>

#include<cstring>

#include<iomanip>

#include<cmath>

#include<algorithm>

#include<bits/stdc++.h>

using namespace std;

int N, M;

int num = INT_MAX, sum = ;

int A[][];

bool visit[][];

bool outOfBorder(int i, int j)

 {

    if (i <  || i >= N || j <  || j >= M)

        return true;

    return false;

}

void DFS(int i, int j, int currentSum, int currentNum)

 {

    visit[i][j] = true;

    currentSum += A[i][j];

    ++currentNum;

    if ( * currentSum >= sum)

     {

        if ( * currentSum == sum)// 如果当前遍历过的数字之和等于所有数字之和的一半

            num = min(currentNum, num);// 更新包含左上角格子的那个区域包含的格子的最小数目

        visit[i][j] = false;

        return;// 回溯到上一结点

    }

    if (!outOfBorder(i, j + ) && !visit[i][j + ])// 向右移动

        DFS(i, j + , currentSum, currentNum);

    if (!outOfBorder(i + , j) && !visit[i + ][j])// 向下移动

        DFS(i + , j, currentSum, currentNum);

    if (!outOfBorder(i, j - ) && !visit[i][j - ])// 向左移动

        DFS(i, j - , currentSum, currentNum);

    if (!outOfBorder(i - , j) && !visit[i - ][j])// 向上移动

        DFS(i - , j, currentSum, currentNum);

    visit[i][j] = false;

}

int main(){

  cin>>M>>N;

    for (int i = ; i < N; ++i)

        for (int j = ; j < M; ++j)

        {

            cin>>A[i][j];

            sum += A[i][j];

        }

    DFS(,,,);

    if (num == INT_MAX)

        printf("");// 输出0

    else

        printf("%d",num);

    return ;

}