// Readiz lesson: complete C++17 local exercise.
#include <iostream>
#include <queue>
#include <string>
#include <vector>
using namespace std;
void dfs(int u, const vector<vector<int>>& graph, vector<int>& visited) {
    visited[u] = 1;

    for (int v : graph[u]) {
        if (visited[v]) continue;
        dfs(v, graph, visited);
    }
}

int dfsSizeIterative(int start, const vector<vector<int>>& graph, vector<int>& visited) {
    int size = 0;
    vector<int> stack;

    visited[start] = 1;
    stack.push_back(start);

    while (!stack.empty()) {
        int u = stack.back();
        stack.pop_back();
        size++;

        for (int v : graph[u]) {
            if (visited[v]) continue;
            visited[v] = 1;
            stack.push_back(v);
        }
    }
    return size;
}

vector<int> shortestDistance(int start, const vector<vector<int>>& graph) {
    int n = (int)graph.size();
    vector<int> dist(n, -1);
    queue<int> q;

    dist[start] = 0;
    q.push(start);

    while (!q.empty()) {
        int u = q.front();
        q.pop();

        for (int v : graph[u]) {
            if (dist[v] != -1) continue;
            dist[v] = dist[u] + 1;
            q.push(v);
        }
    }
    return dist;
}

int countComponents(const vector<vector<int>>& graph) {
    int n = (int)graph.size();
    vector<int> visited(n, 0);
    int components = 0;

    for (int i = 0; i < n; ++i) {
        if (visited[i]) continue;
        components++;
        dfs(i, graph, visited);
    }
    return components;
}

vector<vector<int>> gridDistance(
    const vector<string>& grid,
    int sy,
    int sx
) {
    int h = (int)grid.size();
    int w = h == 0 ? 0 : (int)grid[0].size();
    vector<vector<int>> dist(h, vector<int>(w, -1));
    queue<pair<int, int>> q;

    int dy[4] = {-1, 1, 0, 0};
    int dx[4] = {0, 0, -1, 1};

    if (sy < 0 || sy >= h || sx < 0 || sx >= w || grid[sy][sx] == '#') return dist;
    dist[sy][sx] = 0;
    q.push({sy, sx});

    while (!q.empty()) {
        auto [y, x] = q.front();
        q.pop();

        for (int dir = 0; dir < 4; ++dir) {
            int ny = y + dy[dir];
            int nx = x + dx[dir];

            if (ny < 0 || ny >= h || nx < 0 || nx >= w) continue;
            if (grid[ny][nx] == '#') continue;
            if (dist[ny][nx] != -1) continue;

            dist[ny][nx] = dist[y][x] + 1;
            q.push({ny, nx});
        }
    }
    return dist;
}
int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    int h,w,sy,sx,ty,tx;
    if (!(cin>>h>>w>>sy>>sx>>ty>>tx) || h<1 || h>500 || w<1 || w>500 || sy<0 || sy>=h || sx<0 || sx>=w || ty<0 || ty>=h || tx<0 || tx>=w) return 1;
    vector<string> grid(h);
    for (auto &row:grid) {
        if (!(cin>>row) || (int)row.size()!=w || row.find_first_not_of(".#")!=string::npos) return 1;
    }
    if (grid[sy][sx]=='#' || grid[ty][tx]=='#') return 1;
    auto distance=gridDistance(grid,sy,sx);
    cout<<distance[ty][tx]<<'\n';
}