Problem: Berland has n cities, some of them are connected by bidirectional roads. For each road we know whether it is asphalted or not.

The King of Berland Valera II wants to asphalt all roads of Berland, for that he gathered a group of workers. Every day Valera chooses exactly one city and orders the crew to asphalt all roads that come from the city. The valiant crew fulfilled the King's order in a day, then workers went home.

Unfortunately, not everything is as great as Valera II would like. The main part of the group were gastarbeiters — illegal immigrants who are enthusiastic but not exactly good at understanding orders in Berlandian. Therefore, having received orders to asphalt the roads coming from some of the city, the group asphalted all non-asphalted roads coming from the city, and vice versa, took the asphalt from the roads that had it.

Upon learning of this progress, Valera II was very upset, but since it was too late to change anything, he asked you to make a program that determines whether you can in some way asphalt Berlandian roads in at most n days. Help the king.

Input

The first line contains two space-separated integers n, m <image> — the number of cities and roads in Berland, correspondingly. Next m lines contain the descriptions of roads in Berland: the i-th line contains three space-separated integers ai, bi, ci (1 ≤ ai, bi ≤ n; ai ≠ bi; 0 ≤ ci ≤ 1). The first two integers (ai, bi) are indexes of the cities that are connected by the i-th road, the third integer (ci) equals 1, if the road was initially asphalted, and 0 otherwise. 

Consider the cities in Berland indexed from 1 to n, and the roads indexed from 1 to m. It is guaranteed that between two Berlandian cities there is not more than one road.

Output

In the first line print a single integer x (0 ≤ x ≤ n) — the number of days needed to asphalt all roads. In the second line print x space-separated integers — the indexes of the cities to send the workers to. Print the cities in the order, in which Valera send the workers to asphalt roads. If there are multiple solutions, print any of them. 

If there's no way to asphalt all roads, print "Impossible" (without the quotes).

Examples

Input

4 4
1 2 1
2 4 0
4 3 1
3 2 0


Output

4
3 2 1 3


Input

3 3
1 2 0
2 3 0
3 1 0


Output

Impossible

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
#pragma comment(linker, "/STACK:36777216")
template <class T>
inline void RD(T &);
template <class T>
inline void OT(const T &);
template <class T>
inline T &_RD(T &x) {
  RD(x);
  return x;
}
inline int RD() {
  int x;
  return _RD(x);
}
inline void RF(double &x) { scanf("%lf", &x); }
inline double _RF(double &x) {
  scanf("%lf", &x);
  return x;
}
inline double RF() {
  double x;
  return _RF(x);
}
inline void RC(char &c) { scanf(" %c", &c); }
inline char _RC(char &c) {
  scanf(" %c", &c);
  return c;
}
inline char RC() {
  char c;
  return _RC(c);
}
inline void RS(char *s) { scanf("%s", s); }
template <class T0, class T1>
inline void RD(T0 &x0, T1 &x1) {
  RD(x0), RD(x1);
}
template <class T0, class T1, class T2>
inline void RD(T0 &x0, T1 &x1, T2 &x2) {
  RD(x0), RD(x1), RD(x2);
}
template <class T0, class T1, class T2, class T3>
inline void RD(T0 &x0, T1 &x1, T2 &x2, T3 &x3) {
  RD(x0), RD(x1), RD(x2), RD(x3);
}
template <class T0, class T1, class T2, class T3, class T4>
inline void RD(T0 &x0, T1 &x1, T2 &x2, T3 &x3, T4 &x4) {
  RD(x0), RD(x1), RD(x2), RD(x3), RD(x4);
}
template <class T0, class T1, class T2, class T3, class T4, class T5>
inline void RD(T0 &x0, T1 &x1, T2 &x2, T3 &x3, T4 &x4, T5 &x5) {
  RD(x0), RD(x1), RD(x2), RD(x3), RD(x4), RD(x5);
}
template <class T0, class T1, class T2, class T3, class T4, class T5, class T6>
inline void RD(T0 &x0, T1 &x1, T2 &x2, T3 &x3, T4 &x4, T5 &x5, T6 &x6) {
  RD(x0), RD(x1), RD(x2), RD(x3), RD(x4), RD(x5), RD(x6);
}
template <class T0, class T1>
inline void OT(T0 &x0, T1 &x1) {
  OT(x0), OT(x1);
}
template <class T0, class T1, class T2>
inline void OT(T0 &x0, T1 &x1, T2 &x2) {
  OT(x0), OT(x1), OT(x2);
}
template <class T0, class T1, class T2, class T3>
inline void OT(T0 &x0, T1 &x1, T2 &x2, T3 &x3) {
  OT(x0), OT(x1), OT(x2), OT(x3);
}
template <class T0, class T1, class T2, class T3, class T4>
inline void OT(T0 &x0, T1 &x1, T2 &x2, T3 &x3, T4 &x4) {
  OT(x0), OT(x1), OT(x2), OT(x3), OT(x4);
}
template <class T0, class T1, class T2, class T3, class T4, class T5>
inline void OT(T0 &x0, T1 &x1, T2 &x2, T3 &x3, T4 &x4, T5 &x5) {
  OT(x0), OT(x1), OT(x2), OT(x3), OT(x4), OT(x5);
}
template <class T0, class T1, class T2, class T3, class T4, class T5, class T6>
inline void OT(T0 &x0, T1 &x1, T2 &x2, T3 &x3, T4 &x4, T5 &x5, T6 &x6) {
  OT(x0), OT(x1), OT(x2), OT(x3), OT(x4), OT(x5), OT(x6);
}
template <class T>
inline void RST(T &A) {
  memset(A, 0, sizeof(A));
}
template <class T0, class T1>
inline void RST(T0 &A0, T1 &A1) {
  RST(A0), RST(A1);
}
template <class T0, class T1, class T2>
inline void RST(T0 &A0, T1 &A1, T2 &A2) {
  RST(A0), RST(A1), RST(A2);
}
template <class T0, class T1, class T2, class T3>
inline void RST(T0 &A0, T1 &A1, T2 &A2, T3 &A3) {
  RST(A0), RST(A1), RST(A2), RST(A3);
}
template <class T0, class T1, class T2, class T3, class T4>
inline void RST(T0 &A0, T1 &A1, T2 &A2, T3 &A3, T4 &A4) {
  RST(A0), RST(A1), RST(A2), RST(A3), RST(A4);
}
template <class T0, class T1, class T2, class T3, class T4, class T5>
inline void RST(T0 &A0, T1 &A1, T2 &A2, T3 &A3, T4 &A4, T5 &A5) {
  RST(A0), RST(A1), RST(A2), RST(A3), RST(A4), RST(A5);
}
template <class T0, class T1, class T2, class T3, class T4, class T5, class T6>
inline void RST(T0 &A0, T1 &A1, T2 &A2, T3 &A3, T4 &A4, T5 &A5, T6 &A6) {
  RST(A0), RST(A1), RST(A2), RST(A3), RST(A4), RST(A5), RST(A6);
}
template <class T>
inline void CLR(priority_queue<T, vector<T>, less<T> > &Q) {
  while (!Q.empty()) Q.pop();
}
template <class T>
inline void CLR(priority_queue<T, vector<T>, greater<T> > &Q) {
  while (!Q.empty()) Q.pop();
}
template <class T>
inline void CLR(T &A) {
  A.clear();
}
template <class T0, class T1>
inline void CLR(T0 &A0, T1 &A1) {
  CLR(A0), CLR(A1);
}
template <class T0, class T1, class T2>
inline void CLR(T0 &A0, T1 &A1, T2 &A2) {
  CLR(A0), CLR(A1), CLR(A2);
}
template <class T0, class T1, class T2, class T3>
inline void CLR(T0 &A0, T1 &A1, T2 &A2, T3 &A3) {
  CLR(A0), CLR(A1), CLR(A2), CLR(A3);
}
template <class T0, class T1, class T2, class T3, class T4>
inline void CLR(T0 &A0, T1 &A1, T2 &A2, T3 &A3, T4 &A4) {
  CLR(A0), CLR(A1), CLR(A2), CLR(A3), CLR(A4);
}
template <class T0, class T1, class T2, class T3, class T4, class T5>
inline void CLR(T0 &A0, T1 &A1, T2 &A2, T3 &A3, T4 &A4, T5 &A5) {
  CLR(A0), CLR(A1), CLR(A2), CLR(A3), CLR(A4), CLR(A5);
}
template <class T0, class T1, class T2, class T3, class T4, class T5, class T6>
inline void CLR(T0 &A0, T1 &A1, T2 &A2, T3 &A3, T4 &A4, T5 &A5, T6 &A6) {
  CLR(A0), CLR(A1), CLR(A2), CLR(A3), CLR(A4), CLR(A5), CLR(A6);
}
template <class T>
inline void CLR(T &A, int n) {
  for (int i = 0; i < int(n); ++i) CLR(A[i]);
}
template <class T>
inline void FLC(T &A, int x) {
  memset(A, x, sizeof(A));
}
template <class T0, class T1>
inline void FLC(T0 &A0, T1 &A1, int x) {
  FLC(A0, x), FLC(A1, x);
}
template <class T0, class T1, class T2>
inline void FLC(T0 &A0, T1 &A1, T2 &A2) {
  FLC(A0), FLC(A1), FLC(A2);
}
template <class T0, class T1, class T2, class T3>
inline void FLC(T0 &A0, T1 &A1, T2 &A2, T3 &A3) {
  FLC(A0), FLC(A1), FLC(A2), FLC(A3);
}
template <class T0, class T1, class T2, class T3, class T4>
inline void FLC(T0 &A0, T1 &A1, T2 &A2, T3 &A3, T4 &A4) {
  FLC(A0), FLC(A1), FLC(A2), FLC(A3), FLC(A4);
}
template <class T0, class T1, class T2, class T3, class T4, class T5>
inline void FLC(T0 &A0, T1 &A1, T2 &A2, T3 &A3, T4 &A4, T5 &A5) {
  FLC(A0), FLC(A1), FLC(A2), FLC(A3), FLC(A4), FLC(A5);
}
template <class T0, class T1, class T2, class T3, class T4, class T5, class T6>
inline void FLC(T0 &A0, T1 &A1, T2 &A2, T3 &A3, T4 &A4, T5 &A5, T6 &A6) {
  FLC(A0), FLC(A1), FLC(A2), FLC(A3), FLC(A4), FLC(A5), FLC(A6);
}
template <class T>
inline void SRT(T &A) {
  sort(A.begin(), A.end());
}
template <class T, class C>
inline void SRT(T &A, C B) {
  sort(A.begin(), A.end(), B);
}
const int MOD = 1000000007;
const int INF = 0x3f3f3f3f;
const long long INF_64 = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-8;
const double OO = 1e15;
const double PI = acos(-1.0);
template <class T>
inline void checkMin(T &a, const T b) {
  if (b < a) a = b;
}
template <class T>
inline void checkMax(T &a, const T b) {
  if (b > a) a = b;
}
template <class T, class C>
inline void checkMin(T &a, const T b, C c) {
  if (c(b, a)) a = b;
}
template <class T, class C>
inline void checkMax(T &a, const T b, C c) {
  if (c(a, b)) a = b;
}
template <class T>
inline T min(T a, T b, T c) {
  return min(min(a, b), c);
}
template <class T>
inline T max(T a, T b, T c) {
  return max(max(a, b), c);
}
template <class T>
inline T min(T a, T b, T c, T d) {
  return min(min(a, b), min(c, d));
}
template <class T>
inline T max(T a, T b, T c, T d) {
  return max(min(a, b), max(c, d));
}
template <class T, class C>
inline T min_cp(T a, T b, C cp) {
  return min(a, b, cp);
}
template <class T, class C>
inline T min_cp(T a, T b, T c, C cp) {
  return min_cp(min_cp(a, b, cp), c, cp);
}
template <class T, class C>
inline T min_cp(T a, T b, T c, T d, C cp) {
  return min_cp(min_cp(a, b, cp), min_cp(c, d, cp), cp);
}
template <class T, class C>
inline T max_cp(T a, T b, C cp) {
  return max(a, b, cp);
}
template <class T, class C>
inline T max_cp(T a, T b, T c, C cp) {
  return max_cp(max_cp(a, b, cp), c, cp);
}
template <class T, class C>
inline T max_cp(T a, T b, T c, T d, C cp) {
  return max_cp(max_cp(a, b, cp), max_cp(c, d, cp), cp);
}
template <class T>
inline T sqr(T a) {
  return a * a;
}
template <class T>
inline T cub(T a) {
  return a * a * a;
}
int Ceil(int x, int y) { return (x - 1) / y + 1; }
inline bool _1(int x, int i) { return x & 1 << i; }
inline bool _1(long long x, int i) { return x & 1LL << i; }
inline long long _1(int i) { return 1LL << i; }
inline long long _U(int i) { return _1(i) - 1; };
template <class T>
inline T low_bit(T x) {
  return x & -x;
}
template <class T>
inline T high_bit(T x) {
  T p = low_bit(x);
  while (p != x) x -= p, p = low_bit(x);
  return p;
}
template <class T>
inline T cover_bit(T x) {
  T p = 1;
  while (p < x) p <<= 1;
  return p;
}
inline int count_bits(int x) {
  x = (x & 0x55555555) + ((x & 0xaaaaaaaa) >> 1);
  x = (x & 0x33333333) + ((x & 0xcccccccc) >> 2);
  x = (x & 0x0f0f0f0f) + ((x & 0xf0f0f0f0) >> 4);
  x = (x & 0x00ff00ff) + ((x & 0xff00ff00) >> 8);
  x = (x & 0x0000ffff) + ((x & 0xffff0000) >> 16);
  return x;
}
inline int count_bits(long long x) {
  x = (x & 0x5555555555555555LL) + ((x & 0xaaaaaaaaaaaaaaaaLL) >> 1);
  x = (x & 0x3333333333333333LL) + ((x & 0xccccccccccccccccLL) >> 2);
  x = (x & 0x0f0f0f0f0f0f0f0fLL) + ((x & 0xf0f0f0f0f0f0f0f0LL) >> 4);
  x = (x & 0x00ff00ff00ff00ffLL) + ((x & 0xff00ff00ff00ff00LL) >> 8);
  x = (x & 0x0000ffff0000ffffLL) + ((x & 0xffff0000ffff0000LL) >> 16);
  x = (x & 0x00000000ffffffffLL) + ((x & 0xffffffff00000000LL) >> 32);
  return x;
}
int reverse_bits(int x) {
  x = ((x >> 1) & 0x55555555) | ((x << 1) & 0xaaaaaaaa);
  x = ((x >> 2) & 0x33333333) | ((x << 2) & 0xcccccccc);
  x = ((x >> 4) & 0x0f0f0f0f) | ((x << 4) & 0xf0f0f0f0);
  x = ((x >> 8) & 0x00ff00ff) | ((x << 8) & 0xff00ff00);
  x = ((x >> 16) & 0x0000ffff) | ((x << 16) & 0xffff0000);
  return x;
}
long long reverse_bits(long long x) {
  x = ((x >> 1) & 0x5555555555555555LL) | ((x << 1) & 0xaaaaaaaaaaaaaaaaLL);
  x = ((x >> 2) & 0x3333333333333333LL) | ((x << 2) & 0xccccccccccccccccLL);
  x = ((x >> 4) & 0x0f0f0f0f0f0f0f0fLL) | ((x << 4) & 0xf0f0f0f0f0f0f0f0LL);
  x = ((x >> 8) & 0x00ff00ff00ff00ffLL) | ((x << 8) & 0xff00ff00ff00ff00LL);
  x = ((x >> 16) & 0x0000ffff0000ffffLL) | ((x << 16) & 0xffff0000ffff0000LL);
  x = ((x >> 32) & 0x00000000ffffffffLL) | ((x << 32) & 0xffffffff00000000LL);
  return x;
}
using namespace std;
class bignum {
  friend istream &operator>>(istream &, bignum &);
  friend ostream &operator<<(ostream &, const bignum &);
  friend bignum operator+(const bignum &, const bignum &);
  friend bignum operator-(const bignum &, const bignum &);
  friend bignum operator*(const bignum &, const bignum &);
  friend bignum operator/(const bignum &, const bignum &);
  friend bignum operator%(const bignum &, const bignum &);
  friend bignum operator+(const bignum &, const int &);
  friend bignum operator-(const bignum &, const int &);
  friend bignum operator*(const bignum &, const int &);
  friend bignum operator/(const bignum &, const int &);
  friend bignum operator%(const bignum &, const int &);
  friend bool operator==(const bignum &, const bignum &);
  friend bool operator!=(const bignum &, const bignum &);
  friend bool operator<(const bignum &, const bignum &);
  friend bool operator>(const bignum &, const bignum &);
  friend bool operator<=(const bignum &, const bignum &);
  friend bool operator>=(const bignum &, const bignum &);
  friend bool operator==(const bignum &, const int &);
  friend bool operator!=(const bignum &, const int &);
  friend bool operator<(const bignum &, const int &);
  friend bool operator>(const bignum &, const int &);
  friend bool operator<=(const bignum &, const int &);
  friend bool operator>=(const bignum &, const int &);
  friend int do_comp(const bignum &, const int &);
  friend int do_comp(const bignum &, const bignum &);
  friend void divide(const bignum &, const bignum &, bignum &, bignum &);
  friend bignum pow(bignum, int);

 public:
  inline bignum(){};
  inline bignum(int s) {
    while (s != 0) {
      data.push_back(s % 100000000);
      s /= 100000000;
    }
    if (data.empty()) data.push_back(0);
  }
  inline bignum(long long s) {
    while (s != 0) {
      data.push_back(int(s % 100000000));
      s /= 100000000;
    }
    if (data.empty()) data.push_back(0);
  }
  inline bignum(string s) {
    int t, i;
    data.clear();
    for (i = int(s.size()) - 8; i > 0; i -= 8) {
      istringstream(s.substr(i, 8)) >> t;
      data.push_back(t);
    }
    istringstream(s.substr(0, i + 8)) >> t;
    data.push_back(t);
  }
  void operator=(const int);
  void operator=(const string);
  void operator=(const bignum);
  bignum &operator+=(const bignum &);
  bignum &operator-=(const bignum &);
  bignum &operator*=(const bignum &);
  bignum &operator/=(const bignum &);
  bignum &operator%=(const bignum &);
  bignum &operator+=(const int &);
  bignum &operator-=(const int &);
  bignum &operator*=(const int &);
  bignum &operator/=(const int &);
  bignum &operator%=(const int &);
  bignum &operator%=(const long long &);
  bool undefined();
  int do_try(const int &);
  int do_try(const bignum &);
  void do_trim();
  list<int> data;
  void add(const int a) {
    list<int>::iterator it = data.end();
    it--;
    if ((*it) < 10)
      (*it) = a;
    else if ((*it) < 100)
      (*it) = (*it) % 10 + 10 * a;
    else if ((*it) < 1000)
      (*it) = (*it) % 100 + 100 * a;
    else if ((*it) < 10000)
      (*it) = (*it) % 1000 + 1000 * a;
    else if ((*it) < 100000)
      (*it) = (*it) % 10000 + 10000 * a;
    else if ((*it) < 1000000)
      (*it) = (*it) % 100000 + 100000 * a;
    else if ((*it) < 10000000)
      (*it) = (*it) % 1000000 + 1000000 * a;
    else if ((*it) < 100000000)
      (*it) = (*it) % 10000000 + 10000000 * a;
  }
  void clear() { data.clear(); }
  long long t() {
    if (data.size() == 1)
      return *data.begin();
    else {
      list<int>::iterator it = data.begin(), jt = data.begin();
      ++it;
      return (long long)(*it) * 100000000 + (*jt);
    }
  }
  int size() {
    list<int>::iterator it;
    int res = 0;
    for (it = data.begin(); it != data.end(); it++) res += 8;
    it--;
    if (*it >= 10000) {
      if ((*it) >= 1000000) {
        if (*it >= 10000000)
          ;
        else
          res--;
      } else {
        if ((*it) >= 100000)
          res -= 2;
        else
          res -= 3;
      }
    } else if ((*it) >= 100) {
      if (*it >= 1000)
        res -= 4;
      else
        res -= 5;
    } else {
      if ((*it) >= 10)
        res -= 6;
      else
        res -= 7;
    }
    return res;
  }
  void do_reserve(int a) {
    if (a <= 0) return;
    list<int>::iterator it;
    for (it = data.begin(); it != data.end() && a > 0; it++) a -= 8;
    if (it == data.end() && a >= 0) return;
    a += 8, it--;
    int f = 1;
    for (int i = 0; i < a; i++) f *= 10;
    (*it) %= f;
    data.erase(++it, data.end());
    do_trim();
  }
  void output() {
    list<int>::reverse_iterator i = data.rbegin();
    printf("%d", *i);
    for (i++; i != data.rend(); i++) printf("%08d", *i);
  }
};
inline void bignum::operator=(const bignum a) {
  data.clear();
  for (list<int>::const_iterator i = a.data.begin(); i != a.data.end(); i++) {
    data.push_back(*i);
  }
}
inline void bignum::operator=(const string a) { (*this) = bignum(a); }
inline void bignum::operator=(const int a) { (*this) = bignum(a); }
inline istream &operator>>(istream &input, bignum &a) {
  string s;
  int t, i;
  input >> s;
  a.data.clear();
  for (i = int(s.size()) - 8; i > 0; i -= 8) {
    istringstream(s.substr(i, 8)) >> t;
    a.data.push_back(t);
  }
  istringstream(s.substr(0, i + 8)) >> t;
  a.data.push_back(t);
  return input;
}
inline ostream &operator<<(ostream &output, const bignum &a) {
  list<int>::const_reverse_iterator i = a.data.rbegin();
  output << *i;
  for (i++; i != a.data.rend(); i++) {
    if (*i >= 10000) {
      if (*i >= 1000000) {
        if (*i >= 10000000)
          cout << *i;
        else
          cout << 0 << *i;
      } else {
        if (*i >= 100000)
          cout << "00" << *i;
        else
          cout << "000" << *i;
      }
    } else {
      if (*i >= 100) {
        if (*i >= 1000)
          cout << "0000" << *i;
        else
          cout << "00000" << *i;
      } else {
        if (*i >= 10)
          cout << "000000" << *i;
        else
          cout << "0000000" << *i;
      }
    }
  }
  return output;
}
inline bool bignum::undefined() { return data.empty(); }
inline int do_comp(const bignum &a, const bignum &b) {
  if (a.data.size() < b.data.size()) return -1;
  if (a.data.size() > b.data.size()) return 1;
  list<int>::const_reverse_iterator i;
  list<int>::const_reverse_iterator j;
  for (i = a.data.rbegin(), j = b.data.rbegin(); j != b.data.rend(); i++, j++) {
    if (*i < *j) return -1;
    if (*i > *j) return 1;
  }
  return 0;
}
inline int do_comp(const bignum &a, const int &b) {
  return do_comp(a, bignum(b));
}
inline bool operator==(const bignum &a, const bignum &b) {
  return do_comp(a, b) == 0;
}
inline bool operator!=(const bignum &a, const bignum &b) {
  return do_comp(a, b) != 0;
}
inline bool operator<(const bignum &a, const bignum &b) {
  return do_comp(a, b) == -1;
}
inline bool operator>(const bignum &a, const bignum &b) {
  return do_comp(a, b) == 1;
}
inline bool operator<=(const bignum &a, const bignum &b) {
  return do_comp(a, b) != 1;
}
inline bool operator>=(const bignum &a, const bignum &b) {
  return do_comp(a, b) != -1;
}
inline bool operator==(const bignum &a, const int &b) {
  return do_comp(a, b) == 0;
}
inline bool operator!=(const bignum &a, const int &b) {
  return do_comp(a, b) != 0;
}
inline bool operator<(const bignum &a, const int &b) {
  return do_comp(a, b) == -1;
}
inline bool operator>(const bignum &a, const int &b) {
  return do_comp(a, b) == 1;
}
inline bool operator<=(const bignum &a, const int &b) {
  return do_comp(a, b) != 1;
}
inline bool operator>=(const bignum &a, const int &b) {
  return do_comp(a, b) != -1;
}
inline void bignum::do_trim() {
  while (data.size() > 1 && data.back() == 0) data.pop_back();
}
inline bignum &bignum::operator+=(const bignum &a) {
  list<int>::iterator i;
  list<int>::const_iterator j;
  int t = 0;
  for (i = data.begin(), j = a.data.begin();
       i != data.end() && j != a.data.end(); i++, j++) {
    *i += *j + t;
    t = *i / 100000000;
    *i %= 100000000;
  }
  while (i != data.end()) {
    *i += t;
    t = *i / 100000000;
    *i %= 100000000;
    i++;
  }
  while (j != a.data.end()) {
    data.push_back(t + *j);
    t = data.back() / 100000000;
    data.back() %= 100000000;
    j++;
  }
  if (t != 0) data.push_back(t);
  return *this;
}
inline bignum &bignum::operator-=(const bignum &a) {
  list<int>::iterator i;
  list<int>::const_iterator j;
  int t = 0;
  for (i = data.begin(), j = a.data.begin(); j != a.data.end(); i++, j++) {
    *i -= t + *j;
    if (*i >= 0)
      t = 0;
    else
      *i += 100000000, t = 1;
  }
  while (i != data.end()) {
    *i -= t;
    if (*i >= 0)
      t = 0;
    else
      *i += 100000000, t = 1;
    i++;
  }
  (*this).do_trim();
  return *this;
}
inline bignum &bignum::operator+=(const int &a) { return (*this) += bignum(a); }
inline bignum &bignum::operator-=(const int &a) { return (*this) -= bignum(a); }
inline bignum operator+(const bignum &a, const bignum &b) {
  list<int>::const_iterator i, j;
  bignum c;
  int t = 0;
  for (i = a.data.begin(), j = b.data.begin();
       i != a.data.end() && j != b.data.end(); i++, j++) {
    c.data.push_back(t + *i + *j);
    t = c.data.back() / 100000000;
    c.data.back() %= 100000000;
  }
  while (i != a.data.end()) {
    c.data.push_back(t + *i);
    t = c.data.back() / 100000000;
    c.data.back() %= 100000000;
    i++;
  }
  while (j != b.data.end()) {
    c.data.push_back(t + *j);
    t = c.data.back() / 100000000;
    c.data.back() %= 100000000;
    j++;
  }
  if (t != 0) c.data.push_back(t);
  return c;
}
inline bignum operator-(const bignum &a, const bignum &b) {
  list<int>::const_iterator i, j;
  bignum c;
  int t = 0;
  for (i = a.data.begin(), j = b.data.begin(); j != b.data.end(); i++, j++) {
    t = *i - t;
    if (t >= *j)
      c.data.push_back(t - *j), t = 0;
    else
      c.data.push_back(t + 100000000 - *j), t = 1;
  }
  while (i != a.data.end()) {
    t = *i - t;
    if (t >= 0)
      c.data.push_back(t), t = 0;
    else
      c.data.push_back(t + 100000000), t = 1;
    i++;
  }
  c.do_trim();
  return c;
}
inline bignum operator*(const bignum &a, const bignum &b) {
  list<int>::const_iterator i, j;
  list<int>::iterator k, kk;
  bignum c;
  long long t = 0;
  for (int i = 0; i < a.data.size() + b.data.size(); i++) c.data.push_back(0);
  for (i = a.data.begin(), k = c.data.begin(); i != a.data.end(); i++, k++) {
    for (j = b.data.begin(), kk = k; j != b.data.end(); j++, kk++) {
      t += (long long)(*i) * (*j) + (*kk);
      *kk = int(t % 100000000);
      t /= 100000000;
    }
    *kk += t;
    t = 0;
  }
  c.do_trim();
  return c;
}
inline int bignum::do_try(const bignum &a) {
  int l = 1, r = 99999999, m, t;
  while (l + 2 < r) {
    m = (l + r) / 2;
    t = do_comp(*this, a * bignum(m));
    if (t == 0) return m;
    if (t < 0)
      r = m - 1;
    else
      l = m;
  }
  while (do_comp(*this, a * bignum(r)) < 0) r--;
  return r;
}
inline void divide(const bignum &a, const bignum &b, bignum &d, bignum &r) {
  list<int>::const_reverse_iterator i = a.data.rbegin();
  int t;
  d = bignum(0);
  r = bignum(0);
  do {
    while (r < b && i != a.data.rend()) {
      d.data.push_front(0);
      r.data.push_front(*i);
      r.do_trim();
      i++;
    }
    if (r >= b) {
      t = r.do_try(b);
      d.data.front() = t;
      r -= (b * bignum(t));
    }
  } while (i != a.data.rend());
  d.do_trim();
}
inline bignum operator/(const bignum &a, const bignum &b) {
  bignum d, r;
  divide(a, b, d, r);
  return d;
}
inline bignum operator%(const bignum &a, const bignum &b) {
  bignum d, r;
  divide(a, b, d, r);
  return r;
}
inline bignum operator+(const bignum &a, const int &b) { return a + bignum(b); }
inline bignum operator-(const bignum &a, const int &b) { return a - bignum(b); }
inline bignum operator*(const bignum &a, const int &b) { return a * bignum(b); }
inline bignum operator/(const bignum &a, const int &b) { return a / bignum(b); }
inline bignum &bignum::operator*=(const bignum &a) {
  (*this) = (*this) * a;
  return *this;
}
inline bignum &bignum::operator/=(const bignum &a) {
  (*this) = (*this) / a;
  return *this;
}
inline bignum &bignum::operator%=(const bignum &a) {
  (*this) = (*this) % a;
  return *this;
}
inline bignum &bignum::operator*=(const int &a) { return (*this) *= bignum(a); }
inline bignum &bignum::operator/=(const int &a) { return (*this) /= bignum(a); }
inline bignum &bignum::operator%=(const long long &b) {
  return (*this) %= bignum(b);
}
inline bignum pow(bignum a, int b) {
  bignum c(1);
  while (b != 0) {
    if (b & 1) c *= a;
    a = a * a;
    b >>= 1;
  }
  return c;
}
inline int rand32() {
  return (bool(rand() & 1) << 30) | (rand() << 15) + rand();
}
inline int random32(int l, int r) { return rand32() % (r - l + 1) + l; }
inline int random(int l, int r) { return rand() % (r - l + 1) + l; }
int dice() { return rand() % 6; }
bool coin() { return rand() % 2; }
template <class T>
inline void RD(T &x) {
  char c;
  for (c = getchar(); c < '0'; c = getchar())
    ;
  x = c - '0';
  for (c = getchar(); c >= '0'; c = getchar()) x = x * 10 + c - '0';
}
template <class T>
inline void OT(const T &x) {
  printf("%d\n", x);
}
const int N = 200;
int mp[N][N];
int n, m;
vector<int> edge[N];
int ans[N];
void init(int x) {
  ans[x] = -1;
  for (int i = 0; i < edge[x].size(); ++i) {
    if (ans[edge[x][i]] != -1) init(edge[x][i]);
  }
}
int gao(int x) {
  int res = ans[x];
  for (int i = 0; i < edge[x].size(); ++i) {
    int go = edge[x][i];
    if (ans[go] != -1 && (mp[x][go] ^ ans[x] ^ ans[go]) != 1) return n + 1;
    if (ans[go] != -1) continue;
    ans[go] = mp[x][go] ^ ans[x] ^ 1;
    int ret = gao(go);
    res = min(n + 1, res + ret);
  }
  return res;
}
void solve() {
  memset(mp, -1, sizeof(mp));
  for (int i = 1; i <= n; ++i) edge[i].clear();
  int mm = m;
  while (mm--) {
    int a, b, c;
    cin >> a >> b >> c;
    if (mp[a][b] != -1 && mp[a][b] != c) {
      printf("Impossible\n");
      return;
    }
    mp[a][b] = mp[b][a] = c;
    edge[a].push_back(b);
    edge[b].push_back(a);
  }
  memset(ans, -1, sizeof(ans));
  int ANS = 0;
  for (int i = 1; i <= n; ++i) {
    if (ans[i] != -1) continue;
    init(i);
    ans[i] = 0;
    int res1 = gao(i);
    init(i);
    ans[i] = 1;
    int res2 = gao(i);
    if (res1 > res2)
      ANS += res2;
    else {
      ANS += res1;
      init(i);
      ans[i] = 0;
      gao(i);
    }
  }
  if (ANS > n)
    printf("Impossible\n");
  else {
    printf("%d\n", ANS);
    bool f = false;
    for (int i = 1; i <= n; ++i) {
      if (ans[i] != 1) continue;
      if (!f)
        f = true;
      else
        printf(" ");
      printf("%d", i);
    }
    printf("\n");
  }
}
int main() {
  while (cin >> n >> m) solve();
}