#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void rset();
void init_test();
void solve();
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed;
  cout.precision(20);
  init_test();
  return 0;
}
template <typename T>
void chmin(T& a, T b) {
  if (a > b) a = b;
}
template <typename T>
void chmax(T& a, T b) {
  if (a < b) a = b;
}
template <typename T>
void MACRO_rdv2_Init(int n, T& t) {
  t.resize(n);
}
template <typename First, typename... Rest>
void MACRO_rdv2_Init(int n, First& first, Rest&... rest) {
  first.resize(n);
  MACRO_rdv2_Init(n, rest...);
}
template <typename T>
void MACRO_rdv2_Scan(int p, T& t) {
  std::cin >> t[p];
}
template <typename First, typename... Rest>
void MACRO_rdv2_Scan(int p, First& first, Rest&... rest) {
  std::cin >> first[p];
  MACRO_rdv2_Scan(p, rest...);
}
template <typename T>
void wrv(const vector<T>& v) {
  for (int(__ii) = (0); (__ii) < (((int)v.size())); ++(__ii)) {
    if (__ii) cout << ' ';
    cout << v[__ii];
  }
  cout << '\n';
}
template <typename T>
void wrm(const vector<vector<T>>& v) {
  for (int(__ii) = (0); (__ii) < (((int)v.size())); ++(__ii)) {
    for (int(__jj) = (0); (__jj) < (v[__ii].size()); ++(__jj)) {
      if (__jj) cout << ' ';
      cout << v[__ii][__jj];
    }
    cout << '\n';
  }
}
template <typename T>
void sc(T& x) {
  cin >> x;
}
template <typename Head, typename... Tail>
void sc(Head& head, Tail&... tail) {
  cin >> head;
  sc(tail...);
}
template <typename T>
void wr(const T& x) {
  cout << x << '\n';
}
template <typename Head, typename... Tail>
void wr(const Head& head, const Tail&... tail) {
  cout << head << ' ';
  wr(tail...);
}
template <typename T>
void wrf(const T& x) {
  cout << x << endl;
}
template <typename Head, typename... Tail>
void wrf(const Head& head, const Tail&... tail) {
  cout << head << ' ';
  wrf(tail...);
}
template <typename T>
void debug_out(const T& x) {
  cerr << x << '\n';
}
template <typename Head, typename... Tail>
void debug_out(const Head& head, const Tail&... tail) {
  cerr << head << ' ';
  debug_out(tail...);
}
template <typename... T>
void err(const T&... cod) {
  wr(cod...);
  exit(0);
}
void solve() {
  int n, m;
  sc(n, m);
  chmin(m, 500 * 1000);
  vector<int> a(n);
  for (int(__ii) = (0); (__ii) < (n); ++(__ii)) cin >> a[__ii];
  int o = 0, e = 0;
  for (int(i) = (0); (i) < (n); ++(i)) {
    o += a[i] % 2;
    e += a[i] % 2 ^ 1;
  }
  int ans = 0;
  set<int> seen, avail[2];
  for (int(i) = (1); (i) < (m + 1); ++(i)) avail[i % 2].insert(i);
  for (int(i) = (0); (i) < (n); ++(i)) avail[a[i] % 2].erase(a[i]);
  for (int(i) = (0); (i) < (n); ++(i)) {
    if (seen.count(a[i])) {
      ++ans;
      o -= a[i] % 2;
      e -= a[i] % 2 ^ 1;
      if (o < e) {
        if (avail[1].empty()) err(-1);
        a[i] = *avail[1].begin();
        avail[1].erase(avail[1].begin());
        ++o;
      } else {
        if (avail[0].empty()) err(-1);
        a[i] = *avail[0].begin();
        avail[0].erase(avail[0].begin());
        ++e;
      }
    }
    seen.insert(a[i]);
  }
  for (int(i) = (0); (i) < (n); ++(i)) {
    if (o < e && (a[i] % 2 ^ 1)) {
      if (avail[1].empty()) err(-1);
      ++ans;
      a[i] = *avail[1].begin();
      avail[1].erase(avail[1].begin());
      ++o;
      --e;
    }
    if (o > e && (a[i] % 2)) {
      if (avail[0].empty()) err(-1);
      ++ans;
      a[i] = *avail[0].begin();
      avail[0].erase(avail[0].begin());
      ++e;
      --o;
    }
  }
  wr(ans);
  wrv(a);
}
void init_test() {
  int qq = 1;
  while (qq--) solve();
}
