#include <cstdlib>
#include <string>
#include <fstream>
#include <iostream>

using namespace std;

string read_file(string filename);
void push (World& world, int& i, int j)
bool solve (World& world, int a, int b, int& step_number)

struct City {
    int id; //i
    int road; //j
    struct City* next_city;
};

struct World {
    City* head;
};