#include <list>

using namespace std;

#define MAX_DEPTH 1000
#define MAX_NUMBER 10000000

int A(int n) { return (n + 7) / 2; }
int B(int n) { return n / 2 + 7; }
int C(int n) { return n * 3 - 5; }
int D(int n) { return (n - 5) * 3; }

class T {
public:
    char t; // { _, A, B, C, D }
    int n;
    int L; // pasos
    T *p; // previo
    T(char _t, int _n, int _L, T *_p) { t = _t; n = _n; L = _L; p = _p; }
};

typedef T *pT;

#define lT list<pT>
#define ilT list<pT>::const_iterator

#define Expand(type, F) \
        {                                                            \
            int n = F(t->n);                                         \
            if(n >= 0 && n < MAX_NUMBER && !c[n]) {                  \
                a[l].push_back(new T(type, n, l, t));                \
                c[n] = true;                                         \
            }                                                        \
        }

void main( void ) {

    lT *a = new lT[ MAX_DEPTH ];
    bool *c = new bool[ MAX_NUMBER ];
    for(int i = 0; i < MAX_NUMBER; i++)
        c[i] = false;

    a[0].push_back(new T('_', 2018, 0, NULL));

    while(1) {
        int l = -1;
        while(++l < MAX_DEPTH)
            if(a[l].size() > 0)
                break;
        T *t = a[l].back();
        if(t->n == 2017) {
            printf("Solución encontrada:\n");
            while(t) {
                char *f;
                switch(t->t) {
                case '_': f = "\t%i + 7 = %i\n"; break;
                case 'A': f = "\t(%i + 7) / 2 = %i\n"; break;
                case 'B': f = "\t%i / 2 + 7 = %i\n"; break;
                case 'C': f = "\t%i * 3 - 5 = %i\n"; break;
                case 'D': f = "\t(%i - 5) * 3 = %i\n"; break;
                }
                printf(f, t->p == NULL ? 2011 : t->p->n, t->n);
                t = t->p;
            }
            break;
        }
        a[l++].pop_back();
        if((t->n & 1) == 1) Expand('A', A);
        if((t->n & 1) == 0) Expand('B', B);
        Expand('C', C);
        Expand('D', D);
    }
}