fuga das galinhas

#include <bits/stdc++.h>

using namespace std;

int _x[4] = {0, 1, 0, -1};
int _y[4] = {1, 0, -1, 0};
int n, m, end_x, end_y, begin_x, begin_y;
bool check(int x, int y){
    return x <= n && x > 0 && y <= m && y > 0;
}

int vis[17][17],val[17][17], ans;
void complete(int l, int c, int qnt){
    vis[l][c] = true;
    //val[l][c] = max(val[l][c], qnt);

    if(l == end_x && c == end_y) ans = max(ans, qnt);
    for(int i = 0; i < 4; i++){
        int x = l + _x[i];
        int y = c + _y[i];
        if(check(x, y) && !vis[x][y]){
            complete(x, y, qnt + 1);
        }
    }

    vis[l][c] = false;
}
int main(){
    scanf("%d %d", &n, &m);
    n = (n+1)/2;
    m = (m+1)/2;
    scanf("%d %d", &begin_x, &begin_y);
    begin_x = (begin_x + 1)/2;
    begin_y = (begin_y + 1)/2;
    scanf("%d %d", &end_x, &end_y);
    end_x = (end_x + 1)/2;
    end_y = (end_y + 1)/2;

    ans = 0;
    complete(begin_x, begin_y, 0);
    //for(int i = 1; i <= n; i++){
    //    for(int j = 1; j <= m; j++) cout << val[i][j] << " \n"[j == m];
    //}
    printf("%d", 2*ans + 1);
    return 0;
}